If your using the Rom, Press On cheats And enter it only into the code Button. Dont Press the gameshark Button or the Codebreakers. It must be Codes. But Try Getting the Codebreakers because they Always Work. But when I used It For the cookies It Made my game Mess up. So Keep checking your Shops In town To see if you can still buy things after every code because Sometimes it Starts to mess up. Heres Some Boy Level Heart Codes.
Gray-820043C0 FFFF
Rick-82004354 FFFF
Cliff-82004508 FFFF
Kai-82004548 FFFF
doctor-820044C8 FFFF
These are Codebreakers, and the Heart Level is the red Heart But you still Can see the Heart Events it just Takes some time. I hope I helped you out