Just remember this:

If the hotel is going up in a category on March 4, and you make a reservation using points (not point advance) on March 3 or earlier locking in the lower rate, and a reservation is made based on this lower rate: ANY CHANGE of ANY TYPE on or after March 4 will constitute a modification to the reservation causing the rate to be adjusted to the points required for the new cat effective March 4.

Any change including number of pax, length, date, payment method, certificate or points, even check in time.

Basically: once you make a point reservation before March 4 for a hotel going up a cat, DO NOT TOUCH IT AGAIN