You would find that a tour pro would use between 12 and 20 golf balls for a four round tournament.
He didn't play as a professional in the event, he played in the pro-am portion of the event
You would sign a declaration that you are a pro prior to starting the tournament from what ive read.
It is the same scoring system with amateur plays.
Yes, pro golfers can use any colour of golf ball as long as it has been approved for tournament play.
With the exception of the fact that the scores of the pro and the scores of the amateur are combined, the scoring system is the same.
A tour pro would have around a dozen golf balls in there bag per round, just in case. But it is completely up to the player.
He won the Hawaiian Open with an Orange Golf ball.
They are invited to play the tournament, it doesn't cost them a penny. Obviously they have travel and accommodation expenses.