You need to specify an exact model . Bushmaster makes and has made a variety of rifles in this caliber - not just AR-pattern rifles, but also the ACR, M17S, and others. The length varies by model.
$1200
anywhere from $800 - 1200, depending on accessories
The 223 is considered a Short Action rifle.
.223 is considered a short action cartridge.
.223 inches.
Short action.
Not without modification. Some 5.56x45 and .223 Remington rifles have a device available for them which allows them to fire .22 Long Rifle rounds... typically, the device replaces the bolt carrier group.
A rifle with a 5.56x45 chamber can utilise .223 Remington cartridges. A rifle with a dedicated .223 Remington chamber cannot accommodate 5.56x45 cartridges. A rifle with a .223 Wylde chamber can accommodate .223 Wylde, .223 Remington, and 5.56x45, but neither a rifle with a 5.56x45 or a .223 Remington chamber can accommodate the .223 Wylde cartridge.
5.56mm by 45mm long. This is similar to, but not the same as .223
Bushmaster carries a product line of semi-automation pistols and rifles similar to the M4 design. Bushmaster originated in 1973 and is based out of North Carolina.
.223 Remington can be cycled in a 5.56x45 rifle; 5.56x45 should not be cycled in a .223 Remington firearm.
The .22 Long Rifle is a rimfire, whereas the .223 Remington is a centerfire cartridge. The .223 uses a longer 'spitzer' projectile vs. the rounded projectile of the .22 LR. The .223 tends to be a heavier projectile, and has a much higher velocity than the .22 LR.