In the rules they are a lot of things that are not said if there are allowed or they are not. Like is leaving and joining allow?

This is being a heping question.

Yup, its alright :), only if you dont do any glitches while doing so.

Thanks, because my internet was very lagy and disconnected me from the server (i was speedrunning with my friend any% co-op)

Yes, no problem :)