First question: Typically varies from case to case according to what I've seen in the threads here. I got a text message telling me to get ready to trade in my current car (which I did not set up for trade-in by the way when I ordered) and within a week I had a VIN. You'll usually get a text message or email stating that a VIN has been assigned and to get ready for delivery. In some cases, there was no email or text and folks were able to see the VIN in either the MVPA (motor vehicle purchase agreement) or through source code. So just check as often as you can without getting burnt out.
Second question: The 10th digit of the VIN is the model year. N = 2022, P = 2023
Third question: Not using them as my quote from Progressive with additional coverage was really good. Maybe others here who have used Tesla insurance can chime in.
Fourth question: Usually once the delivery date is scheduled, it's locked in. However there are plenty of stories here where the delivery date was changed due to issues with the car being delivered (paint scratches, interior blemish etc). Tesla will usually notify you in case that occurs. My advice is to stay in contact with your SA and let them know what's going on especially with scheduling delivery. They have been very accommodating in my experience. I've also been told that they can push out your delivery once after it's been scheduled so it might be good to be upfront about that with the SA so you don't have to go through a lot just to get your car.