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.
No, Because the light base paint will not show up because the color of the primer overpowers the Light Base Paint.
It is not necessary to use a primer for interior walls, but using one helps with adhesion and smoothness of the paint.
Apply a coat of exterior paint over the interior paint to protect the finish and to discourage mildew growth on the paint film.
Only if the 'flat paint' is water based too.
It is best to use an exterior primer outside, rather than an interior. While, the interior paint will work, it does not have the same protection such as UV protection, and fungicide protection that is found in exterior paints.
No and yes it depends
Either oil or latex primer can be used over interior latex paint.
Yes you can.
It is not necessary to use a primer for interior walls, but using one helps with adhesion and smoothness of the paint.
Apply a coat of exterior paint over the interior paint to protect the finish and to discourage mildew growth on the paint film.
Only if the 'flat paint' is water based too.
It is best to use an exterior primer outside, rather than an interior. While, the interior paint will work, it does not have the same protection such as UV protection, and fungicide protection that is found in exterior paints.
No and yes it depends
I wouldn't. I don't think they would have called it "interior paint " just for fun.
You do NOT use regular paint as primer. It contains none of the qualities of primer.
Latex primer is undoubtedly the quickest drying paint.
It will work over another latex paint, however it won't be as scrubable as a normal top coat, and it won't adhere as well as a paint over a primer. Better to apply the primer, then the paint. If the surface is clean and deglossed though, you really don't need a primer and can coat the surface with a quality wall paint.
It would if you put on a good latex primer first.