Yes, they have the ability to un-block a user.
There's no way for a Supervisor to know unless the contributor either deletes the warning message or responds to the message on the Supervisor's talk page.
Yes, all users, regardless if they're a supervisor or not, will have a contributor level badge. This could be a contributor, bronze, silver, gold, platinum, double platinum, or ruby level badge.
Like most of our records, supervisor HisPowr4U was the first...along with being the first Ruby contributor. Who knows what heights this supervisor can achieve?
You have to contact a supervisor/authority on the site in question.
Self-promotion is allowed on a contributor's Profile page but never in an answer. Most likely the contributor is a robot. Most robots will be blocked from the site by a Supervisor. If you are a contributor, you should report your finding to a Supervisor, who will deal with it accordingly. However, if it is a normal contributor, the user will be warned by a Supervisor to stop advertising in answers. If the user does not heed the warning, their account will be suspended. WikiAnswers is a Q&A site, and it not to be used for advertising.
If you're a Supervisor, go to their profile and click "Unblock."
If you believe that your answer is correct, but a contributor keeps spamming/changing the answer, let a supervisor know. They may be able to protect the question, and/or block the contributor.
Contributor badges are earned by simply answering questions, editing answers etc. Supervisor badges are given (by a higher supervisor) when someone is nominated as a category supervisor.
A regular contributor is someone who does not have Supervisor status, or CA status.
If you have a dispute with any contributor, Supervisor or otherwise, please see the 'Dispute Resolution' link in the 'related link' section.
A non-supervisor cannot nominate a contributor for PA themselves. However, they can contact a Supervisor regarding the contributor they wish to nominate. For a list of Supervisors for you to contact, please see the Related Link below.
Probably Chris Whitten, its founder, first contributor, and first administrator.