Can i wear these over my regular prescription glasses?

I would say they are not made to go over glasses. That said, if you have a smaller frame, you could probably make it work. They will sit further away from your eyes if you choose to wear them over glasses. I tried them over a pair of my glasses prior to answering your question. Overall I have found these to be pretty good quality. I’m using these in a healthcare setting while doing exams. They are as good as our hospital provided ones, back when we could actually get them. I’ve been washing them with dish soap, I’ve used one pair for about a week and the plastic is still in pretty good condition. For a single use disposable shield the optical quality of the plastic is what you would expect. These were a good buy, they are all packaged separately, and flat. So storage for 20 pairs is minimal.

Do you sell just the lenses?

This item contains 1 frame+1 shield.

I have a small head 21inch will these be to big?

I believe these should still work for you, the blue plastic frame is very flexible. I would imagine they will wrap around your face more.

How do I get the plastic protective coat off? Can't seem to do this?

personally i didn't find difficulties to get the protective coat off but i don't find this product is practical. I bought for myself and friends but we never use once. It doesn't fit well to the head and nose. Other options on Amazon seems better for me.