Is there any tutorial for setting up and using the pellsson practice rom?

I only really sometimes play minecraft, and usually it's just pvp, so I thought of maybe speedrunning the game to get more into it, what category would be fit for someone like me?

I've seen runners wait on the timer for a specific time then press start, why? An explanation aswell will be appreciated.

I've seen people get p speed earlier in 1-2, but I'm having trouble for some reason, any help or guide

Recently I've been wanting to speedrun super mario world, but all the experience I have with the games is playing a few levels on my snes classic, can I still try speedrunning the game?