The valid and correct I-485 should have only one office to return completed form. Best of luck.

Yes, it is better to resend than do nothing. Good luck

Check the processing times of your application and follow up accordingly.

It is up to visa official to determine if family bonding is a valid reason to extend visa.

It is better to contact the embassy officials to confirm the nature of the backlog.

Yes, you can sponsor your spouse and a cosponsor may be required.

Yes, you may renter the US as an F-1 with a new valis I-20.

Yes you need a separate I-684 for your spouse and stepson.

The information you provided is insufficient to answer your question. A myriad of documents is relevant in adjudicating the I-485. In other words,...

The geographical location of the embassy/consulate is not the problem. The problem may be your friend does not meet the criteria for a visitor...