What constitutes "wrongful" hesitation in bridge?
I believe that cases 1-3 are all ethical, but these are simple problems that should have been solved at the end of some earlier trick (In duplicate bridge, after all the cards to a trick have been faced, players should indicate that they are thinking about the hand by keeping their card face up. Play does not proceed until all players have turned their cards face down.).

None of 1-3 damage declarer, and in any case you may pause to think whenever you have an actual bridge problem. However, your hesitations may also transmit unauthorized information to your partner, and so your partner may be constrained in their future actions.

Jeff Goldsmith has a useful and interesting discussion about unauthorized information on his website, which covers this area, and discusses what you should do in case partner has accidentally given you unauthorized information.