Go on to the guides section, under where it says leaderboard. You'll find a guide on how to play the game there

You can submit a run no matter how bad it is so but if it's under a certain time video proof is required. You can find that under the category rules for the category you are running. As for doing a glitchless run, there's no specific "glitchless" category mostly due to the fact that apart from the OoB (Out of Bounds) major glitch, there isn't a lot of complex glitches, so the "No OoB" or "No R-Pumping" category's are as close as your gonna get to glitchless. Don't worry though, the glitches featured in both of those category's are few and far between, and fairly simple to perform