YES !
Someone totaled one of mine earlier this year and it still had free supercharging miles, not unlimited just some unused free miles since I largely charge at home. When I ordered a new car and used another members code I still had the miles from the first car and the new miles from the code on the second car. Note I kept the totaled car on my Tesla.com account for the time being. But I wiped all personal info from the totaled car.
Also you get thrown into a monthly drawing when you use the code as well.
You can use your own code but you won't get double benefits. If you use someone else's code both people get the benefit.
Insurance will reimburse for Autopilot / FSD as well. You can show them screenshot of the app and your credit card. They did with me. They won't reimburse for supercharging miles as they don't reimburse for "gas" in a totaled ICE car.
For what it's worth:
Earn Free Supercharging Miles or a $100 Cash Award
jeremy75603