@Zap2000: It is really not easy to keep track of your questions if you scatter them all over so many threads (and sometimes the same questions simultaneously to the 3DS Noob Paradise). It is difficult for anybody to answer and it is difficult for you as well because you might get lost yourself (with the answers also scattered).
I’ll try to summarize this a bit although your questions have been answered already (for future reference).
Q: What size of (micro)-SD can I use?
A: It does not matter. But format cards larger than 32GB with FAT32 (on Windows with
guiformat). Test your SD-card(s) with h2testw before using/trusting.
Q: Is it possible to do the hacking process with a small (4GB) card?
A: Yes. And this questions is already answered in the
FAQ of the guide.
Q: What is the best filesystem for the 3DS?
A: The 3DS only supports FAT32 (And maybe FAT16 but so small SDs are practically useless). Format SD-cards with guiformat and choose 32KB cluster size. On cards from 128GB on you might also use 64KB clusters.
The exFAT filesystem will not work.
Q: Why are there two formats for 3DS games? Which one to choose?
A: *.CIA (
CTR
Importable
Archive) files are used to install 3DS games on the internal (micro-)SD of the console.
*.3DS are 1:1 copies from cartridges and can be used with the help of flashcards (like Syk3DS+) and the Citra emulator. Citra can import *.cia, too.
Q: Which way to choose when hacking a 3DS? Is Soundhax better than ntrboot or Frogminer? What is the best way? Are there different results?
A: No matter which path you choose, the goal and the result are always the same:
Install B9S and Luma. If your are on a supported firmware 3.0.0<=Your device<=11.3 Soundhax, is a very easy and fast way.
Buying a flashcard like the R4i Gold 3DS Plus has the advantage of nearly 100% compatibility with the library of *.nds ROMs, while
TWiLight Menu++ (nds-bootstrap) has become very good, but does not have 100% compatibility. And newer ROMs need to be
patched because of Anti-Piracy “features”.
Q: Do I create and link a Nintendo ID before or after hacking?
A: Not really important. You do not need a Nintendo ID for the 3DS anyway (unless you want to download demos or free to play games – like Steel Diver: Sub Wars for Frogminer.) Linking a Nintendo ID requires you to update to latest firmware.
Q: Do I have to avoid future official updates?
A: Short answer: No. Slightly longer answer: Wait a few days if Nintendo releases another update and read here on GBAtemp. If there are any problems, you will automatically see them.
Q: Should I link the same Nintendo ID to the 3DS that I use on my Wii U
A: For the unlikely case of a ban, use separate IDs.
Q: What to do in order to avoid bans?
A: Do not cheat online and do not play games before they are officially released. Do not set your favorite app to some homebrew.
Q: I did not see anything about NAND-backups?! Do we use NAND-backups on the 3DS?
A: Yes, NAND-backups are important! And it is on the
finalizing page.
I hope I did not miss anything important.