You don't get back the paid versions of in app donations that upgraded your app. You are at the mercy of emails to the app creator as to whether you get the ad free version again. Just don't donate to these apps. Pay for the non-free apps, by all means. I wish that the developers would just make their apps either free or put a price on the ad free version. I will not "donate" another thin dime to app creators (I WILL pay for your apps if Google Play offers a pay version, but I will NOT donate for the extended version again).