Jumping in extremely late to this thread, but I have a save file with everything unlocked, including the secret song.
Anyone who just wants to get past a few songs can use these AR codes to guarantee an automatic A+(++) rank on any song they...
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi