Does trim have to be the same throughout the house? Can I have white trim in the living room and natural cherry wood trim in the connecting kitchen?

I have unfinished wood cabinets in my kitchen that have had some markers used on them by a few small children. I have tried to sand some of it off and it does get lighter but is still there. So I decided it is probably better to just paint them.

What temp should the walls be before painting interior rooms? House right now is at 50 degrees.

How do I paint a doorway that has wood stained trim on the outside and on the inside I am painting the trim- which was stained. How do I separate the stained from the painted?

What kind of primer should I use to go from oil base paint to latex?

What size tip to spray a door with oil base?

While removing my wallpaper some of the paper from the wall board tore off. There is one place where the paper is completely gone but most places still have paper but the exterior smooth part of the paper is gone. What should I do to prep these areas for painting?