When I pay $15 for a score report, does that mean all of my AP scores will be sent to a particular university or only one score will go to the designated uni?
All your AP scores (current and past) will be sent to the university.
and you can’t withhold scores from previous years right? So it’s all or nothing?
You can either withhold AP scores ($10 extra per score per college) from the score report, or cancel the AP score completely (no fee but deletes the score from your AP records).
that applies even for the previous AP scores? I heard it’s gotta be before June 15th of the same year you took the exam
Yes, even for previous AP scores. When you take AP exams as a senior, you’ll designate which college will receive your AP score report in July (since you’ll enroll at your college by May 1). You just have to request the score withholding or score cancellation (of any current or previous scores) before June 15 of senior year for it to be effective.