In general, homeschool credits and life-experience classes will not be credited toward AS's course requirements. If courses have been taken through another correspondence course, again, it's best to call and check with Student Services as to whether or not they will be transferred over. It's our understanding that, in general, courses taken at an accredited institution will be accepted. These tests can be done open book, also. Most will finish the entire course from beginning to end in 3 years or less.
Most students simply send in the exam and continue on.
The exception MAY be the mathematics courses. In those cases, many will go ahead and complete the exams and simply hold on to them, continuing through the course, until the graded exams are returned. In our case, I would simply check my son's work and as long as it seemed fine, we sent them in and continued on. If you are concerned, you simply, as mentioned, could hold onto the exams until the previous graded ones are returned. If you've chosen one and wish to switch to the other, it's a fairly simple matter of contacting student services.