Unity collision detection questions

Hey I've been getting into unity the past few weeks and I have a few questions about collision detection.

Can you do collision detection such that you can see when a shot to the head vs body vs gun occurs?

It seems like Unity doesn't really want you to use mesh collision on animated models.

Also if the model animates and I have a sphere collider for his head and his head moves forward relative to his body, will the sphere collider stay with the head?

Also I want to have a character that shoots his hand and have it be attached with a chain to his body. Like it would suddenly become a ball attached to the model's arm with a chain, and it would also retract in at which point it would become a normal hand again. Is this going to be very hard to achieve?

Yes,

You can make colliders with differents tags and get this tag and the unity can tell you what the tag of the collider, the parent of this collider, can tell you even the normal of the collider face.

You don't need to make the colliders based on the meshs, you are free to create and edit them.