Hey, i am trying speedrunning for the first time on a competetive note.

My issue is, i dont know if custom (non copyright music) is allowed in a recording and if yes or no, how does one submit a run? upload it into YT?

To submit a run, you should upload it to a video hosting site (YouTube is best), and then copy the link to your video when you submit a run.

As for custom music in your video, you will have to check the rules of the game you intend to speedrun, and ask the game moderators if the is need. Some games require the in-game music as part of the verification process.

ahhh thank you very much :)