without loooking at others reply:

hand 1:
you need to let it go.
he could easily have a a higher pair than yours.or 56 or at worst he may have something like A3 or A4 dimond in which case you are ahead now,but he has too many outs and you only have two.i would let this go.

Hand two:
depend on the kind of read yo have on him.if he is tight or loose.but a raise of 5BB by MP does not suggest a bigger PP than your QQ to me.i would say make it 3K to play and if he comes over the top you can decide then.i really dont think he has a bigger pair than yours though with that big of a raise.

Hand3:
dont invest any more in this hand,your almost deffo behind of all the range of hands the other two guys could have.dont even make a cotinuation bet here cuz i think its just a waist of chips.

hand4:
i dont like just calling here cuz your not closing the action.the last thing you want is just call the raise and the blindes wake up with a monster and come over the top,or even a tricky player squeezes you to make you fold.
its a reraise or fold for me,and seen as i can see any reraise with out getting pot commited here ,its either puch or fold.