In-game reset:
Press L + R + Start + Select during game play.
Invincibility:
Press Left(2), Right(2), Down. Up, Right, Up(3) at the title screen. A no damage option will now be accessible on the options screen.
Round select:
Press Right(2), Left(2), Up, Down, Left, Down(3) at the title screen. The game music will restart to confirm correct code entry. Press Y to select the new game option. Press Y once more to display the round selection option. Note: You may jump to the Boss rounds by enabling this code.