Welcome to the forum
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1. When should I expect to receive my passport back from New York?
Two weeks was what the premium service said but with covid I imagine it will be longer, but how much longer?
The only service you can use for a fiance visa if attending biometrics at an ASC and mailing your passport to New York is the 'Priority Visa for Settlement' service for $766, which has a 30-working day (6-week) processing time, from the date of biometrics (
https://www.vfsglobal.co.uk/us/en/premium-services/priority-visa-for-settlement).
Though it doesn't always get processed within 30 working days - if they are really busy, it can take longer (the service standards processing time for fiance and spousal visas is 95% of all applications processed within 12 weeks and 100% within 24 weeks)
So if your biometrics is 13th October, I wouldn't expect your passport back until late November or early December..
2. Are wedding date is planned for November 21st but unfortunately we realize that we will not be able to do that date. So we are trying to get an idea of how far we should push the wedding back December or January?
You shouldn't really book anything for the wedding until you have received the visa, as you don't know when you will actually be able to get to the UK and get married... or if the visa will even be issued.
So I would either cancel any bookings you have (if you can) and rebook once you are in the UK, or if you can't cancel, I would push the wedding back as far as you can.
If you will be marrying in England or Wales, you will both need to be resident in the county where you will marry for 7 days before you can give notice to marry (and you must both give notice in person), then you have to wait 28 days after giving notice before you can marry... but this may be extended to 70 days if have a visa and your case is referred to UKVI (that hopefully shouldn't happen with a fiance visa though as UKVI will have already given you permission to marry).
If you will be marrying in Scotland, you don't need to wait the 7 days before giving notice, and you can give notice by post, but you do still need to wait at least 28 days between giving notice and getting married (possibly extended to 70 days if they refer your case to UKVI).