Debug mode
At the title screen press in order the following buttons: right, X, down, up, B, R, X, and START 
After succeeding, the "Push Start Button" will turn red.

Music and Sound
At the title screen press in order the following buttons: press L, right, B, down, L, R, left, and START

Debug mode
If you push X while pushing LR when there's no unit on the map, the map will be cleared. In the same way, if you push A while pushing LR, you'll lose. And if you push LR while the cursor is on the unit, that unit will disappear.