is splits necessary for speedrunning it would be hard for me to press a button to go to the next split because i have a physical disability

Some games are required to have a timer on screen, but a majority of games on the site it isn't required. Although i'm sure there are some games that requires timer if you get a certain place on the leaderboard.

I'm pretty sure most games won't require Livesplit or anything similar, regardless of place in the leaderboard, because you can always time the run afterwards by checking the exact frames of start and finish.

If splits are required find a better game/leaderboard

i am able to start the timer and end it but i would find it hard to go to the next split every couple of minutes

You can configure Livesplit so that the split button will be whatever you want (preferably not a button used in-game). Then again, Livesplit is mainly for you to track your personal progress, not to have an exact timing of a run. You can also have a timer without any splits, so you only have to split at start and end.

You don't need splits, as long as you start and stop at the correct points, you'll be fine. Splits are arbitrary, the purpose of splits is to show you or the viewer how far ahead or behind you are.