Scenario: A commercial app becomes free. The new free version would like to know if the user had purchased the previous commercial version (eg. to unlock things from the get-go). This should work even if the user had uninstalled the previous version (and is now installing the new version.)
Is this possible in any way? In other words, is it possible to find out, for example by quering the App Store, if the user had already purchased the commercial version of the app previously? (The new version can't rely on any data from the old version existing on the device, because it could have been uninstalled. This also wouldn't be the safest way.)