with google play, you have to have the same version number uploaded onto google play website. It can be alfa or beta, not necessary to be live.
In other words, the version you are using on your device have to be uploaded on google play.
IOS is different, you can test it without having it uploaded.
Kinda thought so, and have always done so to be sure. Anyway I am still getting the "Authentication required" message as I try to buy anything. If you see my screenshot, I am getting the "Works" output, so I know it got contact with the store. So the authentication message appears when I click the buy-button. I am sure I have added the products in my "Game services" section. And I don't get this message when I try to buy in app products from other games.