Stage skip:
At the Stage number screen, before the game start, start to press B as fast as you can. If one of the pressings occurs right in time, when to Stage number screen is about to disappear, then the current level will be skipped instantly. If you skip the last level, you'll start from the beginning again. The reason why this doesn't work all the time even with autofire option in emulator is because the button pressing trigger lasts just one frame. If button is held for more than one frame, this trigger is resetting. The game checking exactly the pressings trigger, not the held one. Probably this is just a debug leftover, but maybe just a reward cheat for fastest fingers. ;) To make this cheat reasonable, use Game genie code 9E4?29F?914. With this, the skip button should be held instead and will work all the time.