Yes, you can by using standard tile adhesive.
If by top layer you mean the paper, then re-install drywall on that wall.
Yes, many people do that.
Yes, you can use Kilz over drywall. It is an undercoat, or primer.
Replace the drywall with tile backer.
You can install tile glue right onto drywall. However if you are doing this in a bathroom, first consider all the advantages of using concrete/ fibre boards around the tub and shower. They are far more water resistant, made for tiling, easy to work with and come in handy sizes 30x60 and 36x60. - I have used this in preference to drywall for over 10 years and never had an unhappy client.
Vapour barrier is directly onto studs.
I use basic drywall primer over all of those.
I always have a poly vapour barrier. Better for the drywall.
By painting over with good primer.
There are a few ways that you can repair a large drywall section. One way is to use a patching compound and apply it over the area that needs to be repaired. Another way is to use a drywall adhesive to attach a piece of drywall over the area that needs to be repaired. Cut a piece of drywall to fit the hole. Attach the drywall to the studs with drywall screws. Cover the seams with drywall tape. Cover the entire patch with joint compound. Let the joint compound dry. Sand the joint compound. Paint the patch. For getting the professional drywall patch repair service contact us.
No, you plaster or mud it first.
Rembrandt painted portraits, van Gogh painted over sixty self portraits.