Unlock Sound Test:
Beat the game once to unlock Sound Test.
Unlock Hard Mode:
Beat the game on Normal Mode to unlock Hard mode. This also unlocks Body no. 2 & 3.
Unlock Hell Mode:
Beat the game on Hard Mode.
This cheat can be found on the menu where you select the mini-game of your choice where the girl is standing to the left! Just simply "TOUCH" her! She'll react in different ways depending on where you touch her!
(supplied by: guitarthief1)
Unlock final Body and Feet:
Beat Hell Mode to get final Body and Feet.
(supplied by: sonofreeper)