I finished downgrading from 10.3 an hour or so ago and got up to the EmuNAND tutorial where I was supposed to
"Put the microSD back in your computer. Copy back everything from your backup to your microSD (except NAND.bin), overwriting existing files. Put it in your N3DS again and start it...
I didn't know they made an MSU cart for the Genesis.... I knew about the SNES one and the library for that is rather large but the Genesis one has very few games