Hi Linda, yes, the frame is available for prescription sunglasses. You just need to select Tint/Photochromic/Polarized lens color when you order. 
Tint lenses are permanent and one colour, be it used indoors or outdoors.
Photochromic lenses are transparent indoor while outdoors they darken depending on the light.
Polarized lenses have the same color indoor and outdoor, and the effect is better than tint lenses as they can filter out harmful UV.

Dear customer, so sorry to hear that. We don't have the screw size, however, we can send you a discount coupon to reorder a new pair. Our CSR will reach out to you via email within 24 hours. Please check your inbox or spam mail. Thank you.

It is correct. We measure the total width of the frame from screw to screw. You could measure your old glasses this way: https://www.firmoo.com/help-p-5.shtml. And then choose a pair with similar size to your old glasses. Generally speaking 2 to 3 mm difference is acceptable.

We are sorry that the black one is out of stock. We may not restock the black one recently. If you do not mind, would you like to have a try with another styles? We updated our styles time to time. Please check the new arrivals here: https://www.firmoo.com/new-arrivals.html