Gradius III and IV Cheats

Instant double shot power-up:
Pause the game play after passing the first Boss and press Up(2), Down(2), Left, Right, Left, Right, Square, Triangle. A sound will confirm correct code entry. Note: This may only be up to 25 times, equal to the number of levels that have been successfully completed. Note: To this power-up for player two, press Up(2), Down(2), Left, Right, Left, Right, Square, Triangle, Select, Start.

Instant laser shot power-up:
Pause game play after passing the first Boss and press Up(2), Down(2), Left, Right, Left, Right, X, Circle. A sound will confirm correct code entry. Note: This may only be done up to 25 times, equal to the number of levels that have been successfully completed. Note: To use this power-up for player two, press Up(2), Down(2), Left, Right, Left, Right, X, Circle, Select, Start.

Extra Edit mode:
Successfully complete or accumulate ten hours of game play in Gradius 3 to unlock an "Extra Edit" option. This option allows weapon combinations to be edited. More weapons can be unlocked for editing by completing the game a second time, or by accumulating another ten hours of game play.
Cube Attack mode:
Reach level 9 in Gradius 3 to unlock Cube Attack.
Original Gradius levels:
Intentionally allow a Boss in level 10 in Gradius 3 to hit you to unlock levels from the original Gradius. The original levels will also be unlocked in extra mode.
Boss Rush mode:
Successfully complete Gradius 4 to unlock Boss Rush mode.
Stage select:
Successfully complete Gradius 4 without using any continues to unlock the Stage Select option for that game.