Is it possible to dismiss both the batsmen in ground(ie,by a catch and a run out)?
No. It is not possible to dismiss both batsmen on the same delivery. Only one batsman can be legally dismissed. In the event of both being dismissed on the same delivery, the batsman dismissed first goes back to the pavilion while the other continues with his/her innings.
Is "Hit the ball twice" out?
According to the Laws of Cricket (Law 34 - as stated below), if done intentionally, then yes, it is out.
Law 34 (Hit the ball twice)
1. Out Hit the ball twice
The striker is out Hit the ball twice if, while the ball is in play, it strikes any part of his person or is struck by his bat and, before the ball has been touched by a fielder, he willfully strikes it again with his bat or person, other than a hand not holding the bat, except for the sole purpose of guarding his wicket. See 3 below and Laws 33 (Handled the ball) and 37 (Obstructing the field).
For the purpose of this Law, 'struck' or 'strike' shall include contact with the person of the striker.
However, as with any potential dismissal, the batsman can still continue his/her innings in the following cases:
- The opposition team does not appeal (Law 27.1).
- The appeal is withdrawn by the opposition captain and the umpire consents to the withdrawal, before the batsman leaves the field of play (Law 27.8).
Is it considered a dismissal if the ball hits the other side of the bat?
No. As of the current laws, this does not constitute a dismissal. However, the way the modern bat is designed, the batsmen do not get any advantage by using the other side of the bat. So, it does not make sense for the batsmen to use the other side of the bat.