Replace cracked iOS app with purchased app without losing data I've done jailbreak a few weeks ago to try some new apps and games before buying them.
Today I've updated my iPod touch to a new version and I've purchased some apps I liked. To sync iPod touch with new app I have deleted the previously cracked app and then I realized that all data associated to that app was lost. 

I don't want to loose data from other apps. How can I re-install with purchased version of the same app without loosing data?
If you don't want to wait for an update, there's an easy fix. First install and open up iFile from Cydia. Navigate to /var/mobile/Applications/, tap the gear in the bottom-left corner and make sure "Application Names" is set to On, and then find the app you want to update and/or buy inside that folder. In the app's folder, there will be a file called iTunesMetadata.plist; delete it. Now go to the App Store. Search for the app, and you'll notice that the App Store thinks it's not installed on your device. Click the "Buy App" button and purchase the app. It won't overwrite any of your saved data from the app, and you'll have legally purchased it. This will also work for any apps that you want to reinstall without losing their saved data.