Is 2 player allowed for smo on any of the categories or no?

I personally can’t see why not, it is in Galaxy 1 and 2 so it would make sense to me for it to be allowed

It's not allowed, the reason why its allowed in smg1/2 is because the smg1/2 leaderboards don't split 1p/2p like smo does.

It is allowed, there is a leaderboard for 2P runs. Just keep in mind, if you want to submit to any non-relay category, you must do 2P on your own. Otherwise it is counted as a relay run since you're not doing it on your own.

There is at least one run that actually did SMO Any% with 2P, AnimeeArcade did it in one of our Sandbox Community Races in October 2021. https://www.speedrun.com/multimario/run/z12j5djy

would it be allowed in the all moons smo? since I couldn't find any coop all moons categories

Would it not make more sense to ask in the SMO SRC?

All moons 2p is not possible, because you cant get the Koopa free running moons in 2p

Yeah, no category for that, I think that is mainly down to Volleyball. Kinda bs if you ask me but I think I wouldn't have an issue with it. It's not cheating since you just abuse the opportunity to use a 2nd controller, which the game allows you to do. For us that is just another case of slightly twisting the category rules for Multi Mario I guess, but that's just my view that may not be shared by the other mods.