pre-requisites/math

Are you required to finish taking the med school pre-reqs before you apply to medical school, or before you matriculate? I know that you (obviously) have to take all of the bio, chem, and orgo before taking the MCATs, but can you take classes that are required for medical school (English, math, biochem at a few schools) during your senior year? Or do you have to finish these classes before the end of your junior year when you start applying?

Also, I'm curious as to what medical schools generally count as being a mth class. I have taken a class that is calc 1&2 in one semester here, have also taken a stats class through the psych department, and have a 3 on the AP Calc AB test from high school (that my school did not give me credit for, so it does not show up on my transcripts). Do I need to take another math class, or would either stats of AP credit count as another math class (generally, I know it varies from school to school)? Thank you!