See pbear’s response in #47. Abortion is different from most sins in that there’s an automatic excommunication attached to it. So you not only have to confess, you have to have that excommunication lifted.
Yes, any priest can absolve sins, provided the person making the person confessing has what’s called “purpose of amendment”—i.e., he or she is sorry and really trying to do better. If the priest finds that you are not sorry and have no desire whatsoever to change your ways, he will not absolve you. He will tell you to come back if and when you are ready.
To relate it to John 20, the priest can forgive sin or retain it. It’s pretty uncommon though for a priest to not give absolution.
Oops...my bad, meant to ping pbear8 not PBear. Apologies!
Thanks to both of you for the detailed explanations.