Should the pre-requisites of Sacramental confession, accepting Communion, and prayer for the Pope’s intentions must be completed within a single day in a single church building?
Within seven days, and they do not have to be done in the same church building.
Would the work for which the indulgence is granted (i.e. reading the Bible for at least half an hour) be done within the days when I made the three pre-requisites, or it should be done after them but within the seven days?
It’s best to do them on the same day, but they can all be done on different days within that time frame. The indulgence is earned the moment all the requirements are satisfied.