Yes, you can,and it's very good for that use. However if the concrete is bare, you must apply an epoxy primer before the polyurethane finish.
Yes, as long as the polyurethane is oil-based.
Yes, after allowing a sufficient time for the base to dry.
Cement can wick moisture from outside that will cause your paint to peel off. Look for a primer that will seal it first, then paint it.
I use oil base enamel with oil base polyurethane. Tip: Make sure you allow it to dry completely before you apply top coat. Good luck.
It would if you put on a good latex primer first.
base
Solvent based paint will use a special thinner, and generally be smellier till it dries. Water based paint needs no special thinner and is not smelly.
yes
If you want to keep your paint color pure and cover your object and/or project with 1 or 2 coats, I wouldn't, it sounds like your trying to eliminate a step, I know they do it with stain and polyurethane but not with paint and poly. I think as long as its water-base poly & water-base paint (latex) its possible, try 1oz of paint, 1oz of poly and mix well and try it on a test piece to see if its to your liking. Good-Luck!
Yes, you can.
yes but you cannot put latex on top of oil based surfaces You actually are NOT advised to put oil over latex surfaces, which is why you're supposed to prime will an oil-based (alkyd) primer. Latex and Polyurethane should always have a layer of oil-base beneath it.
no it has a metal and cement base