You must be at the title screen for these codes to work. If you enter them correctly, you'll hear a chime. Start the game and you'll automatically start on that stage.

Code	Effect
I, II, II, II, II, Up	Stage 10
I, I, II, I, I, Down	Stage 11
I, II, I, II, I, Down	Stage 12
I, II, I, I, I, Down	Stage 13
II, II, II, II, I, Down	Stage 14
I, II, I, I, I, Down	Stage 15
II, I, II, I, I, Down	Stage 16
I, I, I, I, I, Down	Stage 17
I, II, II, I, II, Down	Stage 18
II, II, II, II, II, Down	Stage 19
I, II, II, I, II, Up	Stage 2
I, II, II, II, II, Down	Stage 20
II, II, I, II, I, Up	Stage 3
II, I, II, I, II, Up	Stage 4
I, II, II, II, I, Up	Stage 5
II, II, II, I, I, Up	Stage 6
II, I, I, I, I, Up	Stage 7
I, II, II, I, I, Up	Stage 8
I, I, I, II, II, Up	Stage 9