You shouldn't use polyurethane over polyacrylic. Finishes should never be applied over finish, old finish should be sanded and removed first.
I would prime it first.
yes
You can apply "oil" based polyurethane over "oil" based enamel, you can also apply "water" based polyurethane over "water" based enamel, never mix the two, there's to much of a chance for problems.
Decoupage is the art of glueing paper cutouts onto other objects Yes you can polcrylic seal over the paper cutouts
Yes, you can.
No, in fact the wax can ruin the polyurethane finish. Clean the floor with a good wood floor cleaner. Do not mop with water.
That's a common procedure, I haven't had any problems doing it.
You can in some cses, but Minwax does not reccomend it.
Some sort of clear coat, varnish, some sort of polyurethane clear or polycrylic. It creates a hard see-through layer of the clear coat used. It can also be wet-sanded, making it very high gloss.
No! Polyurethane needs a porous surface and because pergo is not, you would only ruin the floor.
A coat of shellac can be placed over polyurethane. You should use de-waxed shellac if you plan on placing more polyurethane on in the future.
Polyurethane will give a long lasting easy to apply finish. Use a water based polyurethane ans clean up will be much easier. You should get years of wear from a good polyurethane finish.
Yes, you can put polyurethane paint over eggshell in latex or eggshell in oil.