As long as none of the paint is flaking, you can.
If your old epoxy is good then you can apply over it, but there are many facts to consider before applying over existing epoxy coating.
You don't normally need sealer over epoxy, but the colour chips may be a reason to. I would check the can for comments on this.
You can definitely use latex paint over epoxy. In fact, it is recommended to use latex over epoxy by the paint manufacturers, rather than using epoxy over epoxy. The latex adheres better and if you then want to use epoxy next time you paint, you have a nice coat of latex between the layers. If you use epoxy over epoxy, often the paint will just peel off in layers once some time passes (and sometimes right away).
The Sharpie will eventually wash off the epoxy. The only way to keep any drawn image on it is to sand it down and do it or possibly draw with your Sharpie and apply a couple coats of epoxy clear coat over it.
Yes, it can.
Yes, it is always necessary when carrying out repairs . The area surrounding the repair is sanded , and the primer patch extends outside the repair onto this "feathered" area. Both epoxy and urethane based primers are suitable.
I wouldn't. I would try to get the first one to cure somehow, possibly by warming that area.
Epoxy primer has to go over a bare surface otherwise it can act as a stripper, causing the base coat, along with the newly applied epoxy to delaminate or lift from the surface.
Thee is no necessity to do that. Any 2 part epoxy is tough enough to withstand anything.
Yes, you can.
Yes, but it may not stay on very well. Besides, epoxy paints are very hard and wear resistant, while latex paints aren't. If the epoxy paint was needed the first time, repainting with something much less durable might not be such a wise move.
Yes. Because a chemical bond is no longer possible because the epoxy coating has dried, a mechanical bond is required. This merely means that the cured epoxy must be lightly sanded before applying the next layer: the first coat should have a matt, nearly white finish.