The console
Whether it be with a NAND backup or the system settings
That are two completely different things.
Restoring the NAND to a known good state can be a solution for certain problems.
In rare cases deleting the current profile can potentially be of use. Most of the time it is a useless sacrifice of personal data. No idea if it fully clears NVRAM for DS(i) mode. As "Format System Memory" makes previously installed software, including their saves unusable (changed encryption key) it is very important to
never use that function without backing up important saves before.
However, both are potentially destructive and should be used with care. "Factory reset" is not a magic solution for all problems – more often than not it creates new problems (as can be seen in the "I accidentally formatted my 3DS"-topics).
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i dont think yall understand the problem i have with the 3ds. im not getting an error message, i cant paly no nds file. everytime i do it flickers a white screen for a second, fades to balck, then it goes back to the home screen. do u understand now
*Sigh* We are not too dumb to understand the problem. Broken DS(i) mode can show a variety of symptoms: Black screens, white screens; we've had a 3DS going to standby each time starting DS software¹. The only time an error message pops up is when the TWL titles are completely missing or if the TWL partition is corrupted. In this case Luma3DS throws an error when trying to reboot into TWLFIRM. I cannot remember a case of going back to Home Menu, but that doesn't mean anything.
"Playing nds files" has potential for misunderstandings. To even come to the point of playing a ROM file the DS(i) mode must be working (TWiLight Menu++ or a flashcart kernel started). To test DS(i) mode while avoiding possible other problems (like bad SD, bad TWL++ installation, bad flashcart…) the easiest thing to do is using preinstalled DS titles (DS Download Play, DS Internet Settings) and/or a legit DS game.
Sadly not all cases of broken DS(i) mode can (yet?) be solved.
yeah. i think where my brother brought it at, i think they did not test it. do yall even understand the issue im trying to say or should i send you all a recording of the problem?
Of course you can upload a video. Why not? Doesn't do any harm.
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¹ That was the long thread "My DS mode is still broken". It turned out the console had a bad camera as well. No idea if this is the reason. I've never tested if DS(i) mode fails without camera.