Nokia X (and X + and XL) is built on Android Project V4.1.2 (level 16). Yes, it is compatible with Xamarin.Android, and you just need to choose the right API level.
It's also interesting to know that Nokia uses Xamarin and MVVM Cross for pre-installed Nokia X applications.
Nokia MixRadio, Windows Phone Windows Store Xamarin, Nokia X . , MVVM- MVVMCross, Nokia X .
Xamarin.