回复：但现在，绿卡父母的已婚子女是不管的，马上结婚是否申请要作废

The old priority date is still valid even after petition is transferred from F2->F1->F3 categories. This is ensured by 8 CFR 1003 federal immigration law (check the law in USCIS website). One thing I want to emphasize is that even some officers and lawyers are not aware of the regulation. SO it is better to spend $200 for a real lawyer to defend your deserved right.