What is the expiation for a vow, an oath, and a covenant in the event of growing a beard and then trimming it before memorizing the Quran, knowing that the vow, oath, and covenant were all for the same thing?

Growing a beard is obligatory. It is not permissible to shave it or trim it so short that it nearly resembles shaving. Your vow concerning growing a beard is a vow to perform an obligation. There is a difference of opinion among scholars regarding its validity. If it is deemed valid, then you are required to pay expiation for having failed to fulfill it. As for your oath, you must pay expiation for breaking it, and a covenant is considered similar to an oath by many scholars. Since the reason for these oaths is the same, the expiations overlap, and you are only required to pay one expiation.