There's a document here which must come with the game: https://cd.textfiles.com/animfestival/GAME/CORNCOB.DOC They do not refer to any such button to be pressed during gameplay, so either it's a secret or it doesn't exist. Maybe someone else will respond, I've never played the game. I has played …

I asking everyone on what's the button for switching back and forth between Standard and Invulnerable Plane in Corncob Deluxe, especially during Gameplay?

Ahem! so what's the button to switch back and forth between Standard and invulnerable plane during missions in Corncob Deluxe?