Adrian Dingle, Author of Crash Course AP Chemistry prep book
In short, way too many answers to give any definitive, one size fits all response.
There are a multitude of variables that come into play here, and I would strongly suggest contacting individual schools, and moreover, individual departments. Policies very WIDELY, with an even wider range of reasons for those policies, including some colleges not wanting you to 'place out' since that has the potential to cost them money!
If I was pushed, obviously 1's and 2's don't count, 3 represents the minimum, and increasingly, if they give credit at all, many of the better schools are looking for 5's only. Having said that, as I have said above, it's a total crapshoot and there is no substitute for talking to individual departments within each school.