So you don't have any rules listed for the timing. So I figured I would go ahead and say some stuff here so that you can add it.

1. The timer starts when you press start on the "1 player" option.
2. The timer ends when the purple screen appears after the final boss.

Do those sound fair? Also, I am practicing this game and I just got a 21'21" so I hope you are prepared to speedrun this game again if I beat your time!