Alright, so I got a code sort of working for Project Mirai DX. I say sort of because if you do not skip the intro movie thing it will freeze your 3DS, but if you keep pressing A to skip it after the "SEGA" logo, you will be fine. Not sure what causes that problem, but it does work:
Code:
[All Songs Max High Score = 2]
D3000000 00000000
C0000000 00000031
006615BC 00000002
006615CC 00000002
006615DC 00000002
006615EC 00000002
006615FC 00000002
0066160C 00000002
0066161C 00000002
0066162C 00000002
DC000000 000000F8
D2000000 00000000