Heroic: Was Avery Junior Johnson a SPARTAN? And, if so, which generation did he belong to and what was it's original project name? Legendary: What were the two biggest improvements that MJOLNIR Mark V had over IV? In addition, how many years was Mark V in service for until it was replaced by Mark VI?

Heroic. Yes, but the project was called orion and was changed to spartan 2 when halsey created the spartan 2 project. He was gen 1. Gen 1 was given significant improvements but nowhere near as drastic as its predecessor. Legendary. The suit was given a shield regenerating shield and was ai capable. As for the time span between v and vi, i wanna say....about 2 months?

Actually, it was close to a year. Mark V was fielded from November of 2551 to October of 2552. And you were correct about the Orions to a good degree. The Orion Project/SPARTAN-I, however, is separate to Halsey's SPARTAN II project. The Orions were the best of the best from the Marine Corps. The SPARTAN II program drew from the genetic best of the best in young children.