This is really laughable. There really isn’t such a thing as an AR15 “pistol.”
There are what are called SBR’s (short-barreled rifles), but as I recall, most of them have 10 inch barrels which isn’t normally what you’d call a pistol.
Yes, there are. And barrels are available as short as 7.5" for them. They don't have stocks, but use a buffer tube coming out the back in order to fit the definition of a pistol.
That's not correct. Bushmaster and others such as Olympic Arms made many auto pistols on the AR platform. I used to own one. They were not SBRs and they did not require a tax stamp. As I recall, the barrel was about 9 inches and did not have a stock. It was cool, but really more of a novelty and kind of useless...just a bullet hose. However, I never heard of one being used in a crime. A few years back Bushmaster was still selling them for around $1000 to $1100.