Titties!
Mad Catz made the Gameshark.
No.
As long as you have the proper codes for your version of the software you shouldn't have any problems getting it to work.
Nintendo i guess
Ebay, Craigslist, used game stores.
Project 64
No where, believe me I've tried to find one myself and there was none except for a N64 gameshark I saw and that was it. Try calling MadCatz for a special order because they still sell gamesharks.
You can turn it on and the red (on) button shows but nothing is shown on the screen.
you open doors by pressing the B button on the controller
Well, on past systems like n64 and genesis, all it was was like the turbo button applied to the start button. As for new systems, i have no earthly idea.
You only have two options Gameshark or Action Replay. I think I would go with the Action Replay because codes are easier to find.