I am sure this question has been asked and answered many times, but I could not find the topic:

How long before or after the due date can either of these be done?

You can apply for an extension during the last 30 days of the 90 day entry. There is no after the 90 days allowed.

Not sure if you're asking just about extending a 90 day stay or extensions and 90 day reports.

90 day reports can be done between 15 days before and 7 days after the due date.

Extensions can be done in last 30 (some offices 45) days of the stay you are going to extend. You can't extend after.