I have an old app (worked just fine with iOS 3 - 8) last updated in 2012 that uses a plist for data. I have since removed that old app from sale because iOS 9 broke it (crashes on launch) and I have no plans to upgrade it since I have another new, very similar, more powerful app in the Store.
The newer app uses Core Data and can export and import (via UTI schemes) the entire Core Data database in order to backup/share the database.
Users of the old app want to transfer their historic data to the new app.
The only way I can think of to accommodate the transfer of data from the old app to the new app, is to create an update of the old app with only one function on one screen that will convert the plist to a Core Data database and email it so it can be imported by the newer app.
Of course that “strategy” may not be allowed by Apple and could allow folks to purchase a non-functioning app and those with a functioning app (< iOS 9) with an update that destroys their app and only exports a database.
So, are there any other ways to take old historical data from one older SKU/bundle identifier to another SKU/bundle identifier?