At 50 km altitude above Venus (where pressure is about 1 bar) you are not really in the "upper atmosphere" as there is still about as much atmosphere above you as on ground level on Earth. So UV radiation is not a problem.
The atmosphere of Venus is just very thick. Also it contains many useful elements, C, O and H, which can be used to build basically anything if you have enough solar energy. The problem is the (comparatively small) amounts of other elements.
The atmosphere of Venus is just very thick. Also it contains many useful elements, C, O and H, which can be used to build basically anything if you have enough solar energy. The problem is the (comparatively small) amounts of other elements.