No. You can only do it on offense.
No, the only times where one can call a timeout is when their team has possession of the ball or when there is a dead ball, which means the clock is stopped (out of bounds, foul called, etc.).
You can call a timeout whenever you would like to.
No you can't.
Yes, the assistant can call a timeout, players on the court can also call timeouts.
they will give you a penalty
The coach can call a timeout
Anytime the team possesing the ball wants to as long as they have time outs left.
a team can call 20 second timeouts or 1 minute timeouts (full)
Coaches or players call timeouts for several reasons. One common reason to call a timeout is to change the momentum of the game. If an opposing player is getting in three-pointer after three-pointer, you might want to call a timeout and hope it disrupts his hot streak. Another reason is to substitute players in. When you want to substitute a player in, the player won't be able to go in until game play stops. Timeouts can do stop a game. Also, another reason to call a timeout is for the coach to tell the players something he wants to say. For example, a coach might call a timeout to tell the players to stop being weak on defense, or to draw up a play when the game is on the line.