I assume you are referring to the hearth and not the interior of the fireplace. If so, the answer is yes. Be sure to give the paint a full seven days to cure before using the fireplace, just to be on the safe side. Some of the benefits of using oil based paint on the hearth is that it will last longer and clean much easier.
What they call "oil base paint" is really called "alkyd base paint." So yes, you can do that.
Yes, you can.
yes
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.
If the base coat used in your project is water base then yes, you bet you can. If there is any chance that the base coat used was an oil base paint then you cannot paint directly over it. The acrylic enamel will not adhere to the oil base paint and will begin to peel off as soon as it is dry. In which case a coat of primer is in order.
What they call "oil base paint" is really called "alkyd base paint." So yes, you can do that.
Don't mix them, your inviting trouble
Yes, you can. You can always paint over with same paint.
Yes, you can.
Yes. Clean and degloss the oil based paint, apply an oil based primer, then apply the water based paint.
Yes, you can
can i use water base paint over oil base paint
yes
Yes, you can, the base is similar.
Yes, you can,
No, you can't .
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.