TL;DR alert! (TL;DR version available on the bottom)
Hello there. I bought an used DSi XL some 3 months ago. Already came with TWiLight Menu++ installed, Unlaunch and I did not notice hiyaCFW there, so I'm assuming it's not installed. I do not have a NAND backup, since it was bought used. System version is 1.4.5U and Unlaunch version is 2.0. I don't know the TWL++ version, but the date on the lower screen was 2017-2021.
This Sunday, while playing Pokémon HeartGold (which I noticed that had this nasty habit of freezing randomly, but not frequently), I travelled down the Cycling Road, where the game really started to freeze a lot, especially after entering battle with the biker at the right side of the bridge. Since I had the habit of saving a lot so as to not lose my progress, I decided to save right as I stepped on the south bank of the Cycling Road, where the game weirdly took a LOT of time to save (more than normal for just a "Saving..." prompt, not the "Saving a lot of data..." one). I almost thought the game had really frozen while saving, but then it finished saving and froze 2 seconds right after doing so. When re-booting the game, I got a notice that my save was corrupted, and that the previous one would be loaded. That's when things REALLY took a big 180°. I managed to get my way out of the Cycling Road and into Fuchsia City, saved, resetted, and that's when I noticed that my face buttons (A, B, X and Y) weren't working. D-pad was fine, and the touchscreen too (since I was searching for items). Prompt for cutting down trees didn't show up, so I used Cut on it from the Pokémon menu. The tree wasn't cut and the Togetic following me got stuck in place, then it began following me, but from way far behind. I resetted the game and tried again, this time avoiding the Cycling Road altogether by going all the way over to the route down Lavender Town. Didn't experience any freezing, but as soon as I started a battle with a trainer, the game froze (keep in mind that during all this time, the game only froze during overworld gameplay, while running around, stationary, etc. It NEVER froze during battles. And sometimes, it didn't even freeze at all, able to play for a long time without getting stuck. I've heard that it's a nds-bootstrap thing).
Resetted the console, then for some reason, all buttons except the Power Button on the Homebrew Launcher menu stopped working. The music slowly faded away and did not boot into the game. Resetted, and then I was able to boot into the game, but then the message "creating save file" appeared on HL's menu. My HG save was still there, and worked fine, until I entered battle, where it froze. Again. Went to sleep and yesterday, I tried playing some other games. Advance Wars worked fine, Pokémon Platinum worked fine (freezing issue there too, especially on the Underground, heard it's a common complaint and associated with nds-bootstrap, but the area I was in did not freeze). Booting into Transformers somehow loaded up Platinum (???) and then the Anti-Piracy warning showed up on HG for some reason. Game booted, okay, but my save wasn't there. It was as if the game did not recognize my save and decided to start from zero. Then after resetting and trying to boot into HG again, I was met with an HL error that I was unable to read because the message ran off-screen, but said I should press B to return (something about "not being able to create..."). Pressed it. The device locked into a black screen while still turned on, and after much fidgetting around, I managed to shut it off by holding the Power Button for 12 secs. I was alleviated to see that it wasn't bricked, but it booted into Unlaunch for some reason. Opening "Launcher" took me to the original DSi menu, where I tried doing the Memory Pit exploit, but wasn't able to. On the Unlaunch menu, there are various instances of TWiLight Menu ++. Boot.nds is nowhere to be seen.
TL;DR version: Starting Sunday, I ran into some completely out of this world behavior in Pokémon HeartGold (a game notorious for freezing out of the blue, but not related to AP, I have almost 40 hours clocked in), then after a bunch of Homebrew Launcher glitches involving the face buttons not working, the HL menu freezing with only the animation of the BG working and lastly, an error message that I was not able to read because it ran off-screen, device got stuck into a black screen, after holding Power Button for 12 seconds, managed to un-freeze it but now stuck on Unlaunch settings and when "Launcher" is booted into, brings me to the DSi original menu. On the Unlaunch menu, there are various instances of TWiLight Menu ++. Boot.nds is nowhere to be seen.
Keep in mind that I was playing during Sunday normally, trying to catch legendaries, do my regular stuff. It was only until I entered the Cycling Road that my problems started. Both Pokémon HG and Platinum NEVER froze during title sections, opening credits, battles, etc.
I am really afraid of doing something wrong here, not familiar AT ALL with the DS platform, and I thought about finding a way to boot back into TWL++, but I am afraid of bricking the console. I can't get another console, this one will have to do. I have two questions though:
1. Is it possible to work my way around this? As someone who had a bit of experience fidgetting around with a PSP, my NDS knowledge is basically zero.
2. If 1 is not possible, is there any way to "wipe the slate clean" without bricking my DS? And if so, should I try to rescue my .sav files from my games, or perhaps they're all corrupted? I think I can give it a shot to try and reinstall everything back.
Will appreciate any helpful answers, thanks.