Depends on your configuration. The most common, by far, is .223 Remington/5.56x45mm NATO.
5.56mm
Yes
Depends on markings on upper.
Depends on the ammo, the range, and the construction of the walls and the armoured cars. Most basic family homes - siding, insulation, drywall - won't even stop a regular handgun round.
The typical AR15 fires the same type of bullet as the M16: a .223 caliber (5.56mmx45mm NATO) round. There are AR-15 rifles that have special barrels made for a variety of popular cartridges, even the little .22LR.
Depends on your configuration. The most common, by far, is .223 Remington/5.56x45mm NATO.
No, a .38 Special cannot shoot a .357 round because the .357 round is longer and more powerful than the .38 Special.
1/2 28
Only 7.62x51. No other 7.62 round is compatible.
.308
Shoot it or run round it
Yes.