Is the MasterDetailPage fully functional on Windows 8.1?
I tried it, and the Master side is closed when you open a Detail page (instead of staying opened like on Android Tablets & iPad).
To reproduce, just try the MasterDetailPageDemoPage in FormsGallery:
https://github.com/conceptdev/xamarin-forms-windows-preview/tree/master/FormsGallery
Note that I did update the project to the latest stable version.