-If so, you have to wait for USCIS to return your child entire I-485 application packet and then, you can mail this original packet back to USCIS ienclosing the USCIS Rejection Notice and the original check (payment) after you fix your child's signature on his/her I-485. USCIS have put a stamp on all of the original documents, so when you return these documents back to USCIS, they may consider this as " 补件".
离孩子的i-94过期还有十几天,保险起见是否file H4做backup。
-Not necessary if you don't want your child to keep the H-4 status. It will be fine even if your child H-4 expires when the I-485 is re-filed.