Hi, is there any chance of Multiplayer% here? Why is it banned? I want to speedrun with 3 other players.

You can post a video of you doing a run here, if we get two submissions in this thread I will add an Any% Multiplayer category and then you can submit your runs there.

Does 'two submissions' mean all players in the run being different of some/all can be the same? Like me doing a run with a few others and some one else doing a run with featuring me.

All players in the runs don't need to be different, as long as both runs don't have the exact same set of people.