Unlimited lives:
Reset the game at the loading screen, then execute the following BASIC commands to restart the program. 

POKE 12865,173
POKE 12957,173
SYS 32768 
Invincibility:
Enter SUMITA at the high score screen. 

Invincibility (alternate):
Load or reset the game, then execute the following BASIC commands before running or restarting the program. 

POKE 12700,96
SYS 32768 
Invincibility (alternate):
Load or reset the game, then execute the following BASIC command before running or restarting the program. 

POKE 12887,96