The amount of credit you can get for AP scores varies greatly from college to college. It really pays to do thorough research. Michigan State, for example, will give you 16 credits for a 5 in a foreign language. At many other colleges you will get only 6 credits.
Yep. At UIUC, you could potentially pick up 20 credit hours for both Japanese and Chinese.
And returning to the subject of UVA, if you get selected as an Echols Scholar, you have no distribution requirements so all of your AP credits are likely to be usable. That makes it very easy to graduate in 3 years, some even do it in 2 or 2.5 years.
Despite the number of AP credits colleges require a certain number of credits taken at (or through counting study abroad I imagine) their school. This also applies to transfer students- eg 60 credits need to be taken at UW (Madison). I guess if you get a degree from a school you need to spend significant time being educated by them.
^ Speaking of which, 3-5 scores get you credit at UW-Madison.
But you still have to satisfy major and distribution requirements.
However, subject credit and advanced placement is more limited at Wisconsin. For many AP scores, a score of 3 gives elective credit, while a score of 4 or 5 is needed for subject credit and advanced placement.