1) File extension application. As long as your application is pending, you may be considered to be in lawful status. An pending extension should not be a problem for filing I-485.
2) To correct I-94. Consult CBP website for the procedure.
2) Third-Country Visa Stamp. It is not recommended. However, for some reason, H-4 really wants to get a new visa stamp, he or she can try Mexico or Canada consulates.