IOS – App Store Promo Codes – What happens if used after a new version is released

No. Apple allows for only a very limited number of promo codes for the lifetime of an application (versions 1.0 - n.0). The exact number escapes me at the moment but somewhere around 100 comes to mind. You are allowed to have more beta testers, but that requires manual management of every user and isn't scalable should you need to go beyond your limit.

At the same time, there are pricing strategies you are free to implement, like free for the first 30 days, holiday and back-to-school sales, and the like.

There is no way to undo a purchase from the end user standpoint, and each user would need to contact apple for a manual adjustment to their account (which might not be something that is even done).

The thing you can control is for that user to set up a second Apple ID to complete a legitimate purchase that qualifies to submit a review. You could also gift the app and be in the clear since that doesn't have the review restrictions that a promotional code redemption does.