After I remove wallpaper can I use a paint with built in primmer and not prime the walls?

Pet stains on wall. Put Kilz oil based original sealer over stains. Do I need to seal entire wall? After painting wall will area sealed be noticeable if I do not seal entire wall ?

My Western steel stainable entry door is peeling because of the sun. How do I removed the old stain with out wrecking the coating on the steel?

I have new construction and contracted to have 2 coats on the exterior of my house. I don’t think there has been 2 coats applied. Is there any way to test for 2 coats?

Bought 2 pre-hung doors and stained them with Minwax. Easy job, but now the wife wants to paint over the stain. Can this be done with regular latex interior paint?