There were two players with that distinction. Pittsburgh Steelers center Mike Webster was given that nickname. He played for the Steelers from 1974-1988. Also former player and head coach Mike Ditka was known as Iron Mike.
No. Mike Tyson was not in the UFC. He was a professional boxer whereas UFC hosts mixed martial arts fights. Mike Tyson was a former undisputed heavyweight boxing champion who was known for his first round knock-outs. Tyson has made multiple appearances in the WWE but has not appeared in the UFC
Evander Holyfield is most well known as a boxer. He was an undisputed heavyweight champion and is perhaps best remembered for defeating Mike Tyson and having part of his ear bitten off in the second fight.
No, he does not. Mike Tyson has been a professionel boxer for several years, and in the professionel boxing world, it is required, that any boxer takes a blood test before the ring match. If mike Tyson was tested HIV positive, he would have lost his boxing license.