I will like to know if it is a foul to take the ball from a player who picks the ball from a rebound and holds it up with two hands? Can the ball be taken from his hands even if they are held high up with both hands?
There is no foul if a defender takes away the ball from a player (who had picked the ball from a rebound and held it with two hands - high or low) without contact. In addition, there may be contact allowed in accordance to Rule 12B Section I (b) below.
From the 2012-2013 NBA Rulebook. Rule 12B Section I (b) states:
Contact initiated by the defensive player guarding a player with the ball is not legal. This contact includes, but is not limited to, forearm, hands, or body check.
There are several exceptions. Here is one relevant to your question:
(5) Incidental contact with the hand against an offensive player shall be ignored if it does not affect the player's speed, quickness, balance and/or rhythm.
e. Contact which occurs on the hand of the offensive player, while that hand is in contact with the ball, is legal.