You are kind of restricted to iOS and Android if you want to release a game that has in apps.
Thank you for your answer.
I thought of a good way.
To have many different add on's for the game that a link opens to the add on downlead to purchase.
Then after the payment they can download the add on and it installs into the game directory.
Other then this I would like to know how they did it.
go look at governor of poker 3, they do exactly this, you can buy all there content in the game.