Yeah, this is the issue; when my original order date was getting close I applied for financing. I think I got around 2.2%. I was happy with this rate as , in general, I can invest that money and get a better rate of return. However, to answer your first question, that rate is only locked in for 30 days.
Since then my delivery date keeps slipping and now I am in 5%+ range. So it's a bit of a balancing act; hits to credit if you keep applying, but locking in a rate (again, 30 days only) that will last until your delivery date.
At this point I am likely to pay cash for the car as I don't like the idea of forking over almost $9k in interest payments to a bank with the current approved rate. Given the current market I doubt I can make my investments beat 6% so I will just pay cash.
In the end, if you have to finance, best to lock in the rate as early as you can to avoid further hikes. This must be balanced with your actual delivery date; I've had two week windows as early as February so my approved 30 day financing has expired (multiple times). Like a dummy I always assumed that "the next delivery date must be good" so I re-applied, only to be disappointed again and again.
Not sure if any of that is helpful but good luck.
*EDIT* Just noted that the exact same car I ordered in Sept '21 now costs $94.9k. These price increases are crazy.