Can you give a certain account a in app purchase for free on your google play app?

Question

So I'm making this game in unity that I'm also publishing on google play. Now I wanted to give a free in app purchase to the first 10 people who donated to me on a different website. So then I emailed them a key, and so there's gonna be a form in the game that asks for the key and then if you submit it gets sent to my dev email.(reason why i'm not just using some file with keys is because I think it's insecure since people could find it) After I review it, then how do I give the user the IAP?

Answer 1

The method that I used in one of my projects was by adding certain codes to my databases on firebase And when the user puts the code you gave him, the script goes to the database and then checks if the code exists and if it does, it deletes it and gives the player the gift so he can't use it more than once.