You press E to swap to the next weapon. I think you just cycle through them instead of there being a back and forth (Q doesn't do anything). I don't know how to punch either. Good luck with this Badge of the Day!
If you make an enemy tank, and then load the code when editing your avatar tank in the game, the enemy won't fire at you while you're free to explore. You can't use the enemy weapons, however, but speed at least can be modified (the only thing useful while doing this).