Cheat mode
You must be on the menu screen that looks like you are on the bridge of the Excelsior to enter the following codes. If done correctly, a text response will appear in the top right corner of the menu.

Level select
At the bridge screen, press Black, R, L, B, X, L, R, Y, White to unlock all levels.

All ships
At the bridge screen, press Black, L, X, L, X, R(2), B, White to unlock all ships.

Invincibility
At the bridge screen, press Black, L, B, L, R, Y(2), B, White.

All medals and ranks
At the bridge screen, press Black, L, R, L, B, R, Y, L, White to unlock all medals and ranks.

Kobayashi Maru difficulty setting
At the bridge screen, press Black, L, Y, L(2), X, Y, R, White to unlock the Kobayashi Maru difficulty setting.