Not without taking some steps. Your best bet will probably be to apply a layer of primer, then after it dries, the new paint.
first paint the walls with an oil based paint then emulsion over the top when dry
Yes, you can
It will work over another latex paint, however it won't be as scrubable as a normal top coat, and it won't adhere as well as a paint over a primer. Better to apply the primer, then the paint. If the surface is clean and deglossed though, you really don't need a primer and can coat the surface with a quality wall paint.
yes you can!
The only capping I know of is the removing the top (caps) from fruit such as strawberries.
Paint the ceiling first. Work top down.
If your dividing the wall the lighter paint should go on top
Not a good idea if you expect it to last. I would strip it, re-prime it properly then paint it.
It's easier if you paint around doors and windows and top and bottom of walls first.
Not without taking some steps. Your best bet will probably be to apply a layer of primer, then after it dries, the new paint.
If by top layer you mean the paper, then re-install drywall on that wall.
I do it first, before painting the wall, with a sash brush, very carefully at the top. The bottom doesn't matter too much as I yet have to paint the wall, but I usually feather it out over 2-3 inches.
19 X 8 - (19 X 1) = You do the math.
first paint the walls with an oil based paint then emulsion over the top when dry
It's not easy to do. I'd hang thin poly sheets from the top edges of the walls if I was doing it.
....is the top of the foundation wall. Simple as that.