I went to the japanese community of SmileBASIC (Petit computer 3) and someone had a post showing a REALLY ACCURATE WINDOWS KNOCKOFF on his 3DS! Does anyone know what that is and/or the code for it?

Yes! So these are all Japanese but here are the most up to date keys: ALPHA OS X: [ P3 S3 EE4X ] The Alpha OS series is the most popular OS on Petitcom3, version X features many new applications AND OS: [1 BWX 7 ENV] This OS is centered around a mobile feel, it's graphics fit your screen perfectly, and has many simple applications, such as a calculator, notepad, timer, and more...

ROKERITE OS: [ 734 KE 3AM ] Similar to Alpha OS, but this one seems to have more apps, its a lesser known OS BENTA OS: [ XEV 47 88E ] A less popular text based OS. ExceedOS: Under development MirrorOS: Under development Phycer OS: Under development Ride OS: Under development