English Learning Android App Development with Sync with Desktop App

I have a Desktop app named as Wonder English. Here is the video demo [login to view URL] Trial is also available: [login to view URL]!AsGdZ4Su6C8liZ9Yb2989C0efNpAQw The Desktop is developed keeping in view the Cross-platform App Development. The database is capable of that. We need an Android App and IOS as well. (xamarin or phonegap) This Desktop app has some problem with the Sync The app and user has a working update method. We moved from sqlite to sqlce with just a update. Apply only if you have read the requirement carefully and answer this, Q: What technology you will use to sync? Q: Do you know mvvm, wpf binding. asynchronous programming. Sync framework. xamarin or phonegap?