As usual , thanks for the detail answer.
JustWatching said:FIFO will be based on the PD.
So whether there is 1,2,4 queues, whichever queue you end up it will be sorted by PD.
The significance of the 45-day letter is two-fold:
1) You don't get to "stand in line" until you have responded.
2) It attempts to clean the application so when it reaches processing, it actually can be processed.