i wanted to ask before i do anything with trying to speedrun other then the 2 mods/code that you guys said could. also could I change sonics skin model for it. it doesn't change anything of how the game works

We do not allow that sorry. For every mod that is supposedly just visuals/audio we'd need to test thoroughly to check if that is actually the case. A lot of work for something without any practical use. Please limit mod use to the two listed mods only.