Mostly the title. I know that it’s likely fine to take the AP’s after you’re admitted, but what a bout after starting school? can I still get credit if I take the AP’s post starting school?
You would need to ask the college/university that you plan to attend about this.
AP exams are only offered once each year. You probably are better off investigating other exams that would award credit a your college/university. Check the website for information about CLEP, DSST, and the others.
Typically, no: APs are specifically oriented towards high school students and are only offered in May, so you would be taking what is meant to be a first year college-level course as (effectively) a second year college student. As @happymomof1 points, CLEP is the college version.