using alt accounts doesn't matter, we have our ways of finding their other accounts
also there aren't any ways to "hack" in the multiplayer of this game (other than causing people to disconnect i guess) what you most likely mean is someone touching the ground and not being disqualified, this is caused by the game having a set maxcontacts setting which is usually 8 or 16, if more collisions than that happen, the game will just ignore them resulting in disqualifications not happening which might look like a "hack" to new players
whenever that happens just ungrab everything and that usually will reduce the amount of collisions enough for the disqualification to register
if you mean something else then feel free to make a thread in the Reports forum with any proof you may have