As prior service MC looking to go AC Navy, is it mandatory I enlist in the RC to request to go AC and if so can my request be denied?

I can't give you a specific answer about Navy recruiting regulations as they are today, but I was a Marine recruiter several years ago. We did take prior service people, but only at certain times, and there was a waiver required. We had to get character references, documentation (DD214, etc.). My experience was that recruiters will try to steer you towards whatever is going to make mission. If they need a HS grad, non prior service contract but not a prior service one, they will try to sell you on something else. I would recommend going to a few different recruiters in different cities and compare what they tell you.