The Full Version of iStudiez Pro for Android allows you to sync on your Android devices only.The Full Version of iStudiez Pro for iOS allows you to sync on your iOS devices only.
If you want to sync the app's data on your computer, you may like to buy the Full Version for Windows/Mac.
And vice versa.
There's no possibility to bundle the purchases from the different Stores.
Thus, the Full Version should be purchased separately on every platform where you'd like to sync.
Otherwise, the app can be used for free without the Cloud Sync service.