Hello, is it possible to hide completely my games (both completed and not) to other people? If yes, how?
No. As far as I know, once a game is started, it can not be undone, hidden or deleted. However you can start a new game as “Private” (by checking appropriate box while creating a game challenge). A private game, once started, can not be undone, revealed to public or deleted (and is necessarily unranked for obvious reason).
I think not even moderators can delete or otherwise tamper with games. I may be wrong, though.
I am not aware of a way to do that — I’d probably be tempted to hide a few of my own games then