It isn't in law. The law simply talks about how you can be in an offside position, that in itself isn't an offence. It becomes and offence when you interfere with with play, interfere with an opponent, or gain an advantage (which is specifically defined as gaining an advantage by playing the...
I would tend to agree with you. But I also think a team gains an advantage when a player is in an offside position and the defence step up expecting the ball to go to him, but he leaves it and a teammate runs on from an onside position to get behind, but again, according to the laws of the game...
1. Right decision. Murray challenged for the ball where the goalkeeper was diving so would be deemed as interfering with an opponent.
2. Right decision from what I can see. Gayle is behind the ball when it is played, so the position of the defenders is irrelevant.
3. Wrong decision...