Currently we have tested 4.2 , 4.3 and 4.5 and they all work.
All games released after March 2013 will force an update to 4.5 (even backup roms).
If a console is lower than 4.2 then it will need to be updated by using an original game released after March 2013.
If a console is between 4.2 and 4.5 then there is no need to update,
but when a newer rom is loaded it will force the update to 4.5 (again fine).
EDIT (2013-08-07): Quote above is old info, according to gateway 3DS website it also works on 4.1.0 too.
As long as you are between 4.1.0 and 4.5.0 you can just use a backup ROM to update to 4.5.0
Note that you won't be able to run backup ROMs that require a firmware version higher then 4.5.0.
3) Your console can be safely updated to 4.5 by using an original title released after
March 2013 till current. Please double check the update message (version) before proceeding !
edit (2013-08-17): sonic2756 has reported success in updating to 4.5.0 using a rom of Luigi's Mansion with Gateway v1.0 loader.
Your 3DS should show the version of the update the game will install in the update message.
Make sure you double check the update version message before going ahead with the update.
The update message looks like this (Thanks Wiki'd for the image): http://i.imgur.com/brrlvRV.jpg
Below is a list of 3DS games that update to firmwares between 4.1.0 and 4.5.0 (Not a complete list)
(Any game released between January 2013 and June 2013 should have an update between 4.1.0 and 4.5.0)
The 3DS console in the "Animal Crossing - New Leaf (USA)" Bundle has 5.1.0U pre-installed. (The game requires 4.5.0U)
Firmware 4.5.0:
Animal Crossing - New Leaf (Europe) [EGDP]
Animal Crossing - New Leaf (USA) [EGDE]
Animal Hospital (Europe) [AZFP]
Chousoku Henkei Gyrozetter - Albatross no Tsubasa (Japan) [ABCJ]
Crash City Mayhem (USA) [AC2E]
Digimon World Re-Digitize Decode (Japan) [ADJJ]
Donkey Kong Country Returns 3D (Europe) [AYTP]
Donkey Kong Country Returns 3D (USA) [AYTE]
Fast & Furious - Showdown (USA) [AFHE]
Fire Emblem - Awakening (Europe) [AFEP]
Games Festival 1 (Europe) [AAEP]
I Love My Pets (Europe) [AA6P]
LEGO City Undercover - The Chase Begins (Europe) [AA8P]
LEGO City Undercover - The Chase Begins (USA) [AA8E]
LEGO Legends of Chima - Laval's Journey (Europe) [APRP]
LEGO Legends of Chima - Laval's Journey (USA) [APRE]
Luigi's Mansion 2 (Europe) [AGGP]
Luigi's Mansion 2 (USA) [AGGE]
Luigi's Mansion 2 (Japan) [AGGJ]
Luxor (Europe) [ALXP]
My Farm 3D (Europe) [ANJP]
Paper Mario - Super Seal (Taiwan) [AG5W]
Pokemon Mystery Dungeon - Gates to Infinity (Europe) [APDP]
Pokemon Mystery Dungeon - Gates to Infinity (USA) [APDE]
Shin Megami Tensei IV (USA) [AMXE]
Tomodachi Collection - Shin Seikatsu (Japan) [EC6J]
Turbo - Super Stunt Squad (Europe) [AANP]
Turbo - Super Stunt Squad (USA) [AANE]
Firmware 4.4.0:
Around the World with Hello Kitty and Friends (Europe) [AHKP]
Brain Age - Concentration Training (USA) [ASRE]
Castlevania - Lords of Shadow - Mirror of Fate (Europe) [ACFE]
Castlevania - Lords of Shadow - Mirror of Fate (USA) (ACFP]
Castlevania - Lords of Shadow - Sadame no Makyou (Japan) [ACFJ]
Croods - Prehistoric Party! (Europe) [AQRP]
Croods, The - Prehistoric Party! (USA) [AQRE]
Dragon Quest VII - Eden no Senshitachi (Japan) [AD7J]
Etrian Odyssey IV - Legends of the Titan (USA) [ASJE]
Fast & Furious - Showdown (Europe) [AFHP]
Fire Emblem - Awakening (USA) [AFEE]
Jewel Master - Cradle of Egypt 2 3D (USA) [AJEE]
Jewel Quest Mysteries - The Seventh Gate (Europe) [AJQP]
Layton Kyouju to Choubunmei A no Isan (Japan) [AL6J]
Magi - Hajimari no Meikyuu (Japan) [ALMJ]
MapleStory - The Girls Fate (Korea) [BMPK]
Mario Tennis Open (USA) [AGAE]
Mario Tennis Open (Taiwan) [AGAW]
Meitantei Conan - Marionette Symphony (Japan) [BKNJ]
Monster High Skultimate Roller Maze (Europe) [AH5P]
Monster High - Skultimate Roller Maze (USA) [AH5E]
Monster Hunter 3 Ultimate (Europe) [AMHP]
Monster Hunter 3 Ultimate (USA) [AMHE]
My Riding Stables 3D - Jumping for the Team (Europe) [AAPP]
Naruto Powerful Shippuden (USA) [AN4E]
New Super Mario Bros. 2 (Taiwan) [ABEW]
Paper Mario - Sticker Star (Europe) [AG5P]
Pokemon no Fushigi no Dungeon - Magnagate to Mugendai no Meikyuu (Japan) [APDJ]
Project X Zone (Europe) [AXXP]
Project X Zone (USA) [AXXE]
Puzzler World 2013 (USA) [AZLE]
Secrets of the Titanic (Europe) [ASEP]
Shin Megami Tensei - Devil Summoner - Soul Hackers (USA) [AHQE]
Shin Megami Tensei IV (Taiwan) [AMXZ]
Sonic & All-Stars Racing Transformed (Europe) [ALLP]
Sonic & All-Stars Racing Transformed (USA) [ALLE]
Super Robot Taisen UX (Japan) [AS6J]
Travel Adventures with Hello Kitty (USA) [AHKE]
Viking Invasion 2 - Tower Defense (Europe) [AVKP]
Zero Escape - Virtue's Last Reward (Europe) [AKGP]
Firmware 4.3.0:
Adventure Time - Hey Ice King! Why'd You Steal Our Garbage! (USA) [AD4E]
American Mensa Academy (USA) [AMME]
Angry Birds Trilogy (Europe) [ANGP]
Art Academy - Lessons for Everyone (USA) [AACE]
Ben 10 - Omniverse (Europe) [ABVP]
Classic Games Overload - Card & Puzzle Edition (USA) [ACGE]
Disney Princess - My Fairytale Adventure (USA) [ADPE]
Fantasy Life (Japan) [AFLJ]
Finding Nemo - Escape To The Big Blue - Special Edition (USA) [AF7E]
Freakyforms Deluxe - Your Creations, Alive! (USA) [ATQE]
Hello Kitty Picnic with Sanrio Friends (Rev 1) (USA) [AHLE] [Note: 'Rev 0' has 4.1.0U]
Hotel Transylvania (USA) [AH8E]
Inazuma Eleven Go 2 - Chrono Stone - Neppuu (Japan) [ANPJ]
Jewel Quest IV - Heritage (Europe) [AJ4P]
Lalaloopsy - Carnival of Friends (USA) [ALYE]
Naruto Powerful Shippuden (Europe) [AN4P]
Naruto SD Powerful Shippuden (Taiwan) [AN4Z]
Paper Mario - Sticker Star (USA) [AG5E]
Pro Evolution Soccer 2013 3D (Europe) [AWTP]
Pro Evolution Soccer 2013 3D (France + Germany) [AWTD]
Pro Evolution Soccer 2013 3D (USA) [AWTE]
Profesor Layton y la Mascara de los Prodigios, El (Spain) [AKKS]
Professeur Layton et le Masque des Miracles (France) [AKKF]
Professor Layton and the Miracle Mask (Europe) [AKKP]
Professor Layton and the Miracle Mask (USA) [AKKE]
Professor Layton und die Maske der Wunder (Germany) [AKKD]
Professor Layton e la Maschera dei Miracoli, Il (Italy) [AKKI]
Puzzler Brain Games (Europe) [AAGP]
Rise of the Guardians (Europe) [ARGP]
Shin Egokoro Kyoushitsu (Japan) [AACJ] (aka: Art Academy - Lessons for Everyone)
Style Savvy - Trendsetters (USA) [ACLE]
Super Black Bass 3D (USA) [ASBE]
Survivor 3D - The Ultimate Adventure (Europe) [AV2P]
The Trash Pack (USA) [ATZE]
Tobidase Doubutsu no Mori (Japan) [EGDJ] {AKA: Animal Crossing - New Leaf}
Wipeout 3 (USA) [AW3E]
Wreck-It Ralph (Europe) [AWRP]
Wreck-It Ralph (USA) [AWRE]
Firmware 4.2.0:
Biohazard - Revelations (Taiwan) [ABRW]
Legend of Zelda, The - Ocarina of Time 3D (Taiwan) [AQEW]
Firmware 4.1.0:
AKB48+Me (Japan) [AKBJ]
Angry Birds Trilogy (USA) [ANGE]
Ben 10 - Omniverse (USA) [ABVE]
Bowling Bonanza 3D (Europe) [AB6P]
Bratz - Fashion Boutique (USA) [AB5E]
Bravely Default - Flying Fairy (Japan) [AFFJ]
Code of Princess (USA) [AC7E]
Danball Senki Baku Boost (Japan) [ADNJ]
Disney Epic Mickey - Power of Illusion (Europe) [AECP] [AECX]
Disney Epic Mickey - Power of Illusion (USA) [AECE]
Disney Princess - My Fairytale Adventure (Europe) [ADPD]
E.X. Troopers (Japan) [ALTJ]
FIFA Soccer 13 (USA) [AF8E]
Finding Nemo - Escape To The Big Blue - Special Edition (Europe) [AF7P] [AF7X]
Freakyforms Deluxe (Europe) [ATQP]
Harvest Moon 3D - A New Beginning (USA) [ABQE]
Hello Kitty Picnic with Sanrio Friends (Rev 0) (USA) [AHLE] [Note: 'Rev 1' has 4.3.0U]
Hotel Transylvania (Europe) [AH8P]
Imagine - Fashion World 3D (Europe) [AF3P]
Imagine - Fashion Life (USA) [AF3E]
Jewel Link - Legends of Atlantis 3D (Europe) [AJ5X]
LEGO The Lord of the Rings (Europe) [ALAP]
LEGO The Lord of the Rings (Germany) [ALAD]
LEGO The Lord of the Rings (USA) [ALAE]
Moshi Monsters - Moshlings Theme Park (USA) [AA9E]
Myst (USA) [AM7E]
New Art Academy (Europe) [AACP]
New Super Mario Bros. 2 (Europe) [ABEP]
New Super Mario Bros. 2 (USA) [ABEE]
Nintendogs + Cats - French Bulldog & New Friends (Taiwan) [ADBW]
Nintendogs + Cats - Shiba & New Friends (Taiwan) [ADAW]
Nintendogs + Cats - Toy Poodle & New Friends (Taiwan) [ADCW]
Pippi Longstocking 3D (Europe) [APEP]
Project X Zone (Japan) [AXXJ]
Rabbids Rumble (Europe) [AR5P]
Rabbids Rumble (USA) [AR5E]
Rise of the Guardians (USA) [ARGE]
Scribblenauts Unlimited (USA) [ASLE]
Sengoku Musou Chronicle 2nd (Japan) [AZCJ]
Sherlock Holmes - The Mystery of the Frozen City (Europe) [AHAP]
Shin Megami Tensei - Devil Survivor Overclocked (Europe) [AMTP]
Spy Hunter (Europe) [AHEP]
Spy Hunter (USA) [AHEE]
Star Fox 64 3D (Taiwan) [ANRW]
Skylanders Giants (Europe) [AG6P]
Skylanders Giants (USA) [AG6E]
Super Black Bass 3D (Europe) [ASBP]
Tohoku Daigaku Karei Igaku Kenkyuusho - Kawashima Ryuuta Kyouju Kanshuu - Monosugoku Nou wo Kitaeru 5-Funkan no Oni Training (Japan) [ASRJ]
Transformers Prime - The Game (Europe) [ATPP]
Zero Escape - Virtue's Last Reward (USA) [AKGE]
The release list at 3ds.essh.co now has the Firmware needed for each release (scroll to the right)
You can use the search box near the top of the page to search for a game or firmware (e.g 4.5.0U / 4.5.0E)
I removed list of games with 5.1.0 and higher, this post only shows games between 4.1.0 and 4.5.0 now.
Last Edit: (2014-03-21): Updated to scene rom #0661.
All that went on sale after March 1 have the update 4.5.0 and 4.4.0 Europe. 3DS Gateway sent me a message and says it works perfectly on the 4.3.0.
Here you have some games with the update (there are many more):
-Castelvania: Lords of Shadow - Mirror of Fate (is what I used)
-Luigi's Mansion Dark Moon
-Monster Hunter 3 Ultimate
-Fire Embelem Awakening
-Lego City Undercover: The Chase Begins
-Pokemon Mystery Dungeon: Gates to Infinity
-Donkey Kong Country Returns 3D
-Animal Crossing New Leaf
- ...
4.5.0 - Animal Crossing - New Leaf (Europe)
4.5.0 - Donkey Kong Country Returns 3D (Europe + USA)
4.5.0 - Fire Emblem - Awakening (Europe)
4.5.0 - LEGO City Undercover - The Chase Begins (USA)
4.5.0 - Luigi's Mansion 2 (Europe)
4.5.0 - Pokemon Mystery Dungeon - Gates to Infinity (USA)
Other regions will 99% likely have the same update, but need confirmation.
I don't think any of these will be cheap since they are all fairly new releases.
Looks like as long as you are between 4.2.0 and 4.5.0 you can just use a backup ROM to update to 4.5.0
Currently it sounds like you won't be able to run backup ROMs that need a firmware higher then 4.5.0.
Some more games that update to firmwares between 4.2.0 and 4.4.0:
4.3.0 - Professor Layton and the Miracle Mask (USA + Europe)
4.3.0 - Paper Mario - Sticker Star (USA)
4.4.0 - Paper Mario - Sticker Star (Europe)
4.4.0 - Monster Hunter 3 Ultimate (USA + Europe)
4.4.0 - Fire Emblem - Awakening (USA)
4.4.0 - Etrian Odyssey IV - Legends of the Titan (USA)
4.4.0 - Mario Tennis Open (USA)
4.4.0 - Castlevania - Lords of Shadow - Mirror of Fate (USA + Europe)
The 3DS Rom Info database will need to have the minimum firmware version added soon too.
YES! I can't believe I have the EXACT version it requires! I already pre ordered mine. In fact, I got an email from Modchipcentral and it said it won't start shipping until August...
I thought they said it was Mid July.
It wasn't too long ago we saw our first glimpse of Courage Reborn, another Twilight Princess PC port in the works based on last year's decompilation efforts. With...
Seemingly out of nowhere a PC port for Pokemon Platinum has surfaced online, bundled alongside the source code for those interested in building and developing it for...
After much speculation, Nintendo has finally followed their competitors in announcing price increases for their hardware.
You can find a breakdown of what's changing...
Airing last night with very little in the way of warning, a brand new Nintendo Direct was aired. Running for 15 minutes in total, it took a moment to celebrate the...
With very little in the way of announcement, Valve has today increased the price of the Steam Deck but some fairly considerable margins. Both of the available models...
As a part of their Financial Results Briefing for the previous year, Nintendo president Shuntaro Furukawa took to the floor to answer key questions around the Switch...
Earlier this year, Sony announced major price increases for the PS5, PS5 Pro, and PlayStation Portal. Now the company is raising prices again, this time for...
We are once again here to tell you about a game leaking before its release, but for once, it's not one published by Nintendo. The game files for Microsoft's upcoming...
Continuing with the great news of Pokémon Platinum getting a native unofficial PC port just a few days ago, today, yet another classic title from the franchise has...
The latest in a growing number of native PC ports, Paper Mario ReCut got its first pre-release build earlier this week. Based on the N64 recompilation toolchain, the...
With very little in the way of announcement, Valve has today increased the price of the Steam Deck but some fairly considerable margins. Both of the available models...
It wasn't too long ago we saw our first glimpse of Courage Reborn, another Twilight Princess PC port in the works based on last year's decompilation efforts. With...
After much speculation, Nintendo has finally followed their competitors in announcing price increases for their hardware.
You can find a breakdown of what's changing...
Airing last night with very little in the way of warning, a brand new Nintendo Direct was aired. Running for 15 minutes in total, it took a moment to celebrate the...
Seemingly out of nowhere a PC port for Pokemon Platinum has surfaced online, bundled alongside the source code for those interested in building and developing it for...
Earlier this year, Sony announced major price increases for the PS5, PS5 Pro, and PlayStation Portal. Now the company is raising prices again, this time for...
As a part of their Financial Results Briefing for the previous year, Nintendo president Shuntaro Furukawa took to the floor to answer key questions around the Switch...
The latest in a growing number of native PC ports, Paper Mario ReCut got its first pre-release build earlier this week. Based on the N64 recompilation toolchain, the...
A whole hour of PlayStation content is on the way, thanks to the latest State of Play showcase. Headlining the stream will be Marvel's Wolverine, alongside a...
For the first time in 13 years, the Call of Duty series will again return to Nintendo's consoles. Set to launch on the 23rd of October, the latest release, Modern...