H1 approval has two parts, top part is the H1 petition, and the bottom part is the COS/EOS decision. If you have the new I-94 which means the EOS approval, you don't need to leave US. If you don't have a new I-94, you will need to reenter with visa stamp to get a new I-94. In this case, if you don't leave US, you will be in AOS and using EAD and not in H1 status.
2. If you both receive new I-94, which means USCIS approved your extended status, you are already in H1/H4 without need to leave US.
2. If you both receive new I-94, which means USCIS approved your extended status, you are already in H1/H4 without need to leave US.