OK, I changed your username. let me know if you want me to change it back

Unplug all your input devices and see if it stops.
Try uninstalling desktop enhancement software, keyboard drivers, or hotkey managers.
This is a known bug for many years and nobody can ever figure it out. Something makes windows send garbage keypresses to windows.

You can also remove the CPU Mode hotkey from config > hotkey config. Click where it says scroll lock and then hit escape

enable boot from firmware and emulate SWIs with bios. we don't know anything about dumping roms; ask google

timing PROBABLY DOES NOT affect what PID is called. but it could.
timing PROBABLY DOES NOT affect which PIDs exist. but it could.
stop wasting your time worrying and go play pokemon.

External bios, firmware, and JIT settings all affect accuracy in some way.
None of that has anything to do with whether your save files will work when transferred to a real cartridge. They will work.

your .dsv files aren't in the states folder unless you put them there. If you did that, there's no telling what else you did and messed up. Don't import backup memory. .DSV already is backup memory, it doesn't need importing. Figure out the right place to put .dsv files, then put them there, then boot the emulator. But your .dsv may already be clobbered with empty data, because of something you did when you were confused. Hope you have backups.

Because it's got to do with the entire path, not just the name of the file. Previously, you were using directories closer to the drive root.  Or rather, previously, you weren't using directories as long as the ones you're using now. To reproduce it I would probably need to know the entire directory you used -- not that there's anything I could do about it, because windows has a limit of 260 characters. But now it's clear the problem isn't the wacky characters.

As a tip for future reference when you get "Pokemon Mystery Dungeon - Explorers of Sky - Hidden Shopkeeper Village (Europe) (Multiboot Demo) (Nintendo Channel).zip" which contains "Pokemon Mystery Dungeon - Explorers of Sky - Hidden Shopkeeper Village (Europe) (Multiboot Demo) (Nintendo Channel).nds", don't dearchive the nds inside the same-named directory, but rather straight into a more normal directory with loose files in it--otherwise the absurd length of the file name counts twice against the limit

Seems like the length of the filenames, or something about the characters in the filenames you're using are too long or too weird. That the same thing basically happens for cheats and saves both is a big clue that it's related to the filesystem + the paths you're using. Maybe the same thing causes flakeouts while loading the roms, without the files being garbage. You could try running it in visual studio and seeing where that crash comes from. But for now I suggest trying to rename them to c:\test\lollers.nds and see if that works (and move desmume into c:\test if needed)

"Demos cannot save." "I can't use saves" <-------- does not compute. Please clarify.

Nobody has made cheats for demos. Whatever cheats you're using are for the wrong game.  They shouldn't work.

As for the crashes, no doubt it's due to it being a (garbage) file with a .nds extension

Citra doesn't matter.
"super fast" "still no lag" isn't technical enough. "2 minutes per turn" was technical enough. The actual framerates would be technical enough.

To lower the HD rendering options, delete your INI file, and pay attention to what you change next time.

Only google knows how to fix your GPU drivers.

Pokemon black is probably a heavier game, maybe your CPU is pathetic.

Is it possible 2 minutes per turn was an exaggeration? I figure that's about 15 seconds per turn normally, which means you're running at 8fps. That seems like a pretty grave dysfunction.

Perhaps you ran things on Desmume like Soul silver without a problem, before your computer got broken. Surely you've tried a different game in order to determine whether your problem with pokemon black was actually a problem with all games? Most likely explanation is you HAVENT, and you increased the HD rendering options or postprocessing filters to an untenable level such that no game will run at full performance; or your system is now broken (most likely in the GPU driver department).

I'm sure it can be done, but it sounds like a job for suuper. I try not to work on the frontend; I'm just waiting til the time is right to put it in bizhawk instead.