Hello folks,
I beg to differ with my fellow companions.
Case 1 : IMO it is a fold out of turn. Player should pay attention to the game, so they should know when they are required to post and when to act. Hand is mucked, player gets a warning.
Case 2 : I agree, if cards are identifiable, player A gets their card back, and a warning for the same reason above.
However, I know which kind of tournament Guillaume is talking about, these tend to not penalize too much because a fair proportion of players are online players and are not used to live tournaments, so in case 1, I may use rule 1 to give the cards back and still issue a friendly warning. (which does not count as a real one)