Cleaning the Ball

Question 1:
In which of these six situations may a player clean their ball when they have lifted it under the Rules?
a) When taking relief under penalty from a water hazard.
b) When taking relief from ground under repair.
c) When requested to lift their ball because it interferes with another player's stance.
d) When dropping a ball in a bunker after taking relief from a hole made by a burrowing animal.
e) When determining if it is unfit for play.
f) When taking relief for a ball embedded in a closely mown area.

Answer 1:
a), b), d) and f).

Part of Rule 21:

A ball on the putting green may be cleaned when lifted under Rule 16-1b. Elsewhere, a ball may be cleaned when lifted, except when it has been lifted:
a. To determine if it is unfit for play (Rule 5-3);
b. For identification (Rule 12-2), in which case it may be cleaned only to the extent necessary for identification; or
c. Because it is assisting or interfering with play (Rule 22).

Question 2:
May a player clean their ball by rubbing it on the putting green?

Question 3:
What is the penalty for cleaning a ball during play of a hole when the Rules do not permit?

Answer 2:
Yes. Decision 16-1d/5. However, this is a bad practice and should be avoided by all golfers.

Note: A player may not rub their ball on the putting green for the purpose of testing the surface of the putting green.

Answer 3:
One penalty stroke. Rule 21.