Need Help.

So I bought an AR15 rifle in January of 2013. It has a bullet button and was legal for when I purchased it. It is a stock mp15 sport. My understanding now is that I need to remove and replace the collapsable stock, flash hider, and pistol grip or I need to register it with the doj. But when I remove and replace those things I can actually put a normal mag release back on.

The rifle is currently in my uncle's name as when we purchased it they were sold out everywhere and we went to a LEO Armory. Can I still transfer it into my name? And also is my understanding of the legality correct?