I ain't trying to tell you what to do. As long as y'all are on the same page, your rules for your competition can be whatever you want.
However, for a standard high score competition (like this thread), the rules are generally simple: no codes, no continues, and you have to physically play (no rubber bands on the controller). Anything else that maximizes score, like milking bosses or purposely dying to replay a level, is fair game.