To make the Apache fire missles on the Title screen, wait until the Helicopter is flying horizontally, and simply press A.
At the campaign select option from the main menu, enter the following codes to unlock subsequent missions.
To see the Secret Opening of the game, press C at the title screen.
Enter ILLBWBY at the password screen .
Enter BQQQAEZ on the password screen to start with 10 lives. You can then re-enter any password to select a level if you wish.
While flying over the ocean's waters in any level, you won't lose any fuel.