Enable Sound Test cheat. Press I, II, than keep pressing Select until the debug screen appears. You can now do the following:

Code - Effect

Use level select to go onto which level you want, then hold I and II and press Start to begin gampleay with 10 lives and 10 bomb - Extra Lives, Bombs, Power

Enter 83 - Half Game with lots of Satellites

Enter 77. Press Up, Down before leaving debug screen. - Invincibility

Enter 00 (level 0) - 09 (level 9) - Level Select