The rules for AF3 can be found by clicking here.
AF3 was an attempt to combine the best features of AF1 and AF2. To do this, it started each day with “Reverse Mode” (AF2) and “Forward Mode” (AF1) with the dismissal process of AF2.
My own experience with using the system for a reasonable period of time was that it didn’t really offer much advantage over using either AF1 or AF2 on its own.
The switching process was a bit clumsy and using AF2 dismissal reduced some of the effectiveness of AF1.
This system was not an improvement over either AF1 or AF2, and has been quietly forgotten.