Does the covenant I made with God to perform daily acts of worship and abstain from certain prohibitions remain valid, after the cancellation of the event to which the covenant was linked?

A covenant with Allah carries the same ruling as an oath (yamin). If you make a covenant with Allah to perform certain acts of worship and abstain from certain things until a specific date, and you fail to fulfill it, then you must offer the expiation for an oath (kaffarat yamin). However, if you made a covenant to do so until a specific event occurs, and this event is cancelled, then the oath is nullified and nothing is binding upon you.