Research indicates that a chambering in 223 Wylde will handle the .223/5.56, BCG should make no difference. As far as I know, they are the same.
Yep, the bolt is the same. It's kind of a hybrid of .223 and 5.56 - IIRC it just has a little more freebore than .223 to allow it to handle 5.56 pressures. I have one AR with that chamber.
Yep. The difference is in the barrel, not the bolt. (My Fulton Armory ARs have Wylde chambers, and they feed everything.)
The .223 Wylde is a proprietary rifle cartridge chamber with the external dimensions and lead angle as found in the military 5.56×45mm NATO cartridge and the 0.2240 inch freebore diameter as found in the civilian SAAMI .223 Remington cartridge. Rifles with a .223 Wylde chamber will typically accept both .223 Remington and externally slightly larger 5.56×45mm NATO ammunition.