-Was it by selection or by election?
-If it was by selection, is it a permanent selection till something happens to the user or a temporary selection that is done periodically?
I think Theymos chooses who becomes moderator. I don't think there is a public ceremony when one becomes moderator.
-Say i aspire to become a moderator someday, is there any possibility to this, and if yes, what are the criteria's for this achievement?
You have to
accurately report a huge amount of spam posts, plagiarism threads e.t.c. you have more chances of becoming a moderator in your local board since you understand the language better than general moderators who may not be from your country. Moderators have a lot of work on their plate, their work load is huge and I don't think they get paid for the work.