Thanks for sharing a valuable point, my son is running 20.
I was thinking that my PD (Apr-2011, EB2) will become current by coming July/Aug-2021 VB under FAD chart, hence his age will be locked and need not switch to F1 later, this is regardless of whether we will receive GC or not before Sep-2021 subject to the USCIS processing capabilities. Please clarify.