You wouldn't have to strip it. You should sand it to roughen for paint and remove any loose paint. Sweep and clean well. Then paint with a good floor paint or garage floor paint kit.
Hi Nancy, if the paint isn't peeling up, then I think you're fine to paint over it. Just be sure to clean it well beforehand.
Yes you can, but it is always best to get up any loose paint first. The finish will not be perfect as you will see thickness of previous colour where colour was stripped back due to flaking, but it is a garage after all and not your sitting room............. If you don't want to see the difference in surface you could try ust painting in the areas that had been stripped of flaked paint and then when dry go over the whole floor.
As long as the paint isn't sealed, you should be fine. Make sure you're using like paint as to what was used prior to ensure it'll stick.
You can if you aren't worried about a perfect finish.
If the paint on the concrete is secure then yes you can paint over it. I would talk to the people at Sherwin Williams. They are very knowledgeable.