2) No appeal
Although this might seem like common sense, an umpire is not allowed to give a batsman out without an appeal from the fielding side. According to Law 27, this does not prohibit a batsman from leaving his wicket without an appeal being made.
The umpire shall intervene if a batsman walks and he is satisfied that the batsman is not out. He will call the batsman back onto the field and signal a dead ball. The appeal from the fielding side can be made any time before the bowler starts his run-up for the next delivery.
The first incident of Mankading happened in 1947 when Indian bowler Vinoo Mankad dismissed Australian Bill Brown; since then a batsman dismissed in this fashion is known to have been Mankaded. The dismissal occurs when the non-striker leaves the crease before the bowler rolls his arm and release the ball.
During the U-19 Wold Cup 2016, West Indies bowler Kemo Paul Mankaded Zimbabwe batsman Richard Nagarava in the last over of a thrilling match. West Indies needed just one wicket while Zimbabwe had to score three runs to qualify for the quarterfinal. But, a clever decision from Paul, who noticed that Nagarava left the crease, changed the course of the tournament as West Indies went on to win the tournament defeating the favourites India.
The MCC (Law 42.15) states that “The bowler is permitted, before entering his delivery stride, to attempt to run out the non-striker. Whether the attempt is successful or not, the ball shall not count as one of the over. If the bowler fails in an attempt to run out the non-striker, the umpire shall call and signal Dead ball as soon as possible.”