Any paint and decorating store should have little pads (like wet-wipes) that you rub onto the painted surface. Whether or not the paint rubs off will tell you what kind of paint was originally used.
With a little alcohol on a cloth, over your finger. Rub it - if color or paint comes off in any way, it's latex or acrylic paint (to be painted over with acrylic or acrylic latex paint).
Yes, oil based paint is very versatile and can be painted over many painted surfaces, including those previously coated with latex paint, as long as the surface is dull and clean.
Acrylic latex paint is a good product, but sits on the surface and does not penetrate. Raw wood and previously oil-based painted surfaces must be primed first to assure adhesion.
No, you either need to really rough up the oil paint with fine sand paper, or put a base coat on before you paint with your Latex paint. If you don't your Latex paint won't adhere.
There are some water based coatings that will adhere to an oil based surface without using a primer; however, an oil or acrylic-based primer, used as a bridge, will allow you to paint latex over an oil-base paint trouble free.
Hot water
Yes it can.
yes but not the other way around the latex passes moisture
Sure, you can fingerpaint it with watercolors if you want to. Won't stick, though.
Acetone is usually used to test if a paint is alkyd or latex, though rubbing alcohol will work as well. Use a Q-tip soaked in either acetone or rubbing alcohol on a surface painted by the paint. If it comes off, it's latex.
Yes, you can.
Yes, you can generally paint high gloss latex over flat latex paint. But you must do all the preparation work in the best tradition of any professional painter. All "flaking" must be removed and the raw wood primed. This will present a "smooth" surface for the new coating. Additionally, everything that is to be painted my be scrupulously clean and free of anything that will restrict the new latex from sticking to the old.
Use a degreaser. Test a small area first to ensure that it won't damage the latex paint also.