Just wanted to know, when different people select different reasons to close a question, what's the reason finally displayed? Is it the one that received the first close vote? What happens for questions closed as a duplicate?
It is whichever receives the most votes for a reason. If it is tied (i.e. 2 as NARQ, 2 not constructive, 1 too localized), then it is the first one to vote. If it's a duplicate that it gets closed as, it (sometimes) lists both duplicates in the question, and that is the reason. If it is voted as OT and sent to another site, it goes there.
For "exact duplicate" votes, if multiple questions are chosen, then all of these links are inserted into the "Possible duplicate:" text on the question. (This was pointed out by slhck in the comments)