As I've mentioned before, this is a classic Trading system problem and the classic solution is to keep your own copy of everything you need. I understand the natural desire to avoid data duplication, but when trading commercially you need to be able to go back and prove who brought what and where it was delivered to.

We should, I believe, keep a full detailed copy of all user information including full name, email and delivery address for each submitted order.

I don't think it's reasonably for an Admin of a store to have to start restoring backups to establish who ordered what and where it was delivered.

When an order is placed it should be thought of as a contract, and you should record all of the details of that contract, so that if a user subsequently changes anything, you can know for certain exactly what their details were at the point when the contract was made.