Gradius III Cheats

Activate the R-Option and collect enough power-ups so that the option selection is highlighted. Now press and hold the A button.

Choose "speed down" for the "!" option in the weapon select screen,
if you can get enough power ups to highlight the last weapon, which will not be visible, and using it without powering up on speed up, you will get all four options, missiles, and the shield. But if you have the laser already, it will be taken away.

Continue to hold A through the initial demo, and you'll see the entire first stage including the boss.

The Final Boss, Bacterion, will die regardless of whether you attack it or not. Just dodge his blasts, and in fifteen or so seconds, he will spontaneously die. Even cheaper, park your ship in the bottom center of the screen, and the shots can't aim towards you!

There are five bonus stages in the game. Here is how to access each one:

<B>Stage 2</B> - When you see a hole in the wall at the bottom of the screen, fly down there.
Prerequisite: None

<B>Stage 3</B> - When you reach the lower level of the stage, there is a platform in the ceiling that drops down. When it drops down, fly just below the part where the platform was.
Prerequisite: Destroy all of the ground targets in the stage up to that point.

<B>Stage 4</B> - In the last set of Moai heads (they look like Easter Island heads), there is one laying down which will lift itself up. Fly behind it.
Prerequisite: Nothing must be highlighted on your powerup bar.

<B>Stage 5</B> - Fly just below the ceiling before the narrow corridor.
Prerequisite: The hundreds digit of your score reads 5, 7, or 3.

<B>Stage 7</B> - Just after the long downward slope in the second half of the level, stay close to the ground and fly into the wall formation shaped like this:
......../
........
____*/

(key: dots are empty space, lines are walls, the asterisk is there your ship should be.).
Prerequisite: Unknown

When you clear a bonus stage, you will end up in the next level. That's right, you don't have to fight the boss of the level you were in previously. However, if you get killed in the bonus stage, you will be taken back to the regular level, and will not be able to reenter the bonus stage.

There is a bonus stage located in the game.
It is located in Level 2. When you fly into the section that is lined with the blue bubbles, look for a hole in the bottom and go in it.