Yes if you upload a photo of yourself...

No, they make the glass for you after you pay and entered your
Prescription. They have a "try on" function were you take a photo and they put the glasses on your face, but it really is not that helpful.

No they have a try on photo app but it is not a accurate reflection of look. If you look at the frames they have a picture of them on other people and i have found that a much more useful tool.

As it's online only, you can't physically try on the frames.
You CAN however upload a picture of your face and the site superimposes an image of the glasses on your face.
It's not as good as physically trying them on, but it gives you an idea of what they'll look like.