回複：回複：Just read this

The I-824 you are describing is for consular processing (while principal doing AOS), not for following to join.
If 1. Child can file I-485 (in US as accompaning BEFORE your I-485 approval) or 2. you can file I-824 for FTJ (AFTER your I-485 approval, bypass NVC, so you cannot file under this class), it's quite clear about the protection (or lack there of) The cutoff date when PD current less I-140 processing time (# of days). For 1. it's secured, child age is frozen (but it did not happen in your case) 2. depending on the date when PD current again.

For I-824 for CP, maybe it's two. You can try and see when NVC will notify.