Well, you'd know if someone has blocked on you on Messenger because when you try and talk to this particular person, the message will not send and it'll say that the person has blocked you.
Now you can not tell the difference if someone is pretending they're offline or if they really offline. But if you have a person who is your friend and you want to know if they're are "offline" they...
All you have to do is go to contacts, tick the box on the left hand side to them and press the button on your keyboard that says delete and a box should come up saying "are you sure you want to...
EDIT: No answer such as ``No``
Maybe these might help ya!
AnimeFaeSunset BitchYeti BitingProbably CacklingDesire CarefullyLovely CaresssAssassin ChickenTear CrazyHorse DaCountingJoker...