Not a good idea, better to use oil based primer.
Yes, you can
Yes, you can,
It's generally much better to use water base primer on drywall.
can i use water base paint over oil base paint
Only if the 'flat paint' is water based too.
You can paint water base paint over an oil based primer after allowing sufficient drying time. Check the instructions on the label because drying times can range anywhere from an hour to 24 hours.
Yes. Clean and degloss the oil based paint, apply an oil based primer, then apply the water based paint.
depending on the surface finish of the primer. Noirmally its matt in its appearance and will take a water based gloss. However, a primer should have an undercoat applied first unless its a primer/undercoat.
yes. However, you cannot use an oil base paint over a latex primer. If you change your mind on the paint, you must strip the paint before you use an oil based paint on the primer.
No, it is not recommended to mix primer and paint together as it can affect the quality and finish of the paint job. It is best to use primer as a base coat before applying paint.
You can always paint latex ( water based )over an oil based paint as the latex just dries on the surface. However don't paint an oil based over a latex paint. Oil based paints need to absorb into the wood or other surfaces or it will just dry and flake off. For more information on the differences and when or not to use a latex or oil paint please see the following article. . http://www.ehow.com/how_4713170_between-latex-oil-base-paint.html
Sure. You can mix them. Why would you? It will not help prime the walls or wood. The primer coat needs to be applied separately to be effective.