Hi @ttcong194 , ok, point by point:
Is it possible for client to join 2 room at same time?
Yes, clients can join as many rooms as you like.
And how to keep track the result from Room2 and send back to Room1 in order to update the result for each client and continue create room2 for winners ?
There's none direct link between rooms but you can use some work around for the flow you are looking for. For example, one way will be (considering you can connect and disconnect to rooms at will):
client connects to room1 > find a match and connects to play in room 2 (disconnects from room1) > after the match finish (let say the client won), you persist the data somewhere (redis, mysql, whatever) > connects back to room1 > but this time the player data will load the last match result.
This would 1 way, you can find tons others (and some probably better).
Hope this helps!