Is it possible to find out who blacklisted me ?

yes

Only if you try to enter one of their giveawas, it will say they blacklisted you.
Also I've seen this question a bunch of times here, maybe try searching the discussions next time instead of creating another thread.

yes, by doing that kind of discussion

yes, but why ?
Blacklists are overrated.

This again? Who really cares? You shouldn't, that's for sure.