Uploading an updated I-864 is not going to cause confusion.....nor will it change the DQ date. You will need to provide latest tax returns, so why not just upload & provide an updated (and better) I-864 at the interview?
My understanding is that consulates release available appointments to NVC once a month. Timing is probably consulate specific. "Available" slots are probably non-immigrant visas and expedites.
1. Case is DQ'd by NVC.
2. Case then enters NVC queue for your consulate and waits at NVC.
3. Consulate informs NVC of available interview date for upcoming month.
4. NVC schedules interviews for cases at the front of the line.
5. NVC schedules your interview when your case reaches the front of the queue for that consulate.
6. NVC notifies person of interview date via email.
7. NVC then sends case to consulate.
After the interview is scheduled, it can take several days to several weeks for the consulate to receive the case.
Spam...or premature. The official USCIS I-129f page does not give that option:
Petition for Alien Fiancé(e) | USCIS
The I-129f is also NOT included in the official list of online USCIS forms:
Forms Available to File Online | USCIS
Your example was for your I-130. No one has ever filed an online I-129F. Maybe the option will come soon.
if the case was already sent from NVC to the wrong consulate, you must contact the CORRRECT consulate and ask them to initiate a transfer. You can also contact the incorrect consulate and inform them.