The appendicular skeleton is attached to the axial skeleton.

Yes, the ribs are part of the axial skeleton.

The axial part of the skeleton is comprised of the bones in the skull and trunk of the body. Yes, the axial part of the skeleton does have a cavity.

Carpals are NOT part of the axial skeleton. The axial skeleton includes the head and trunk. Carpals would be part of the appendicular skeleton which consists of your appendages (arms and legs from the shoulder and hip joints out).

The neck is part of the axial skeleton. The appendicular skeleton includes the bones of your arms and legs.