I have Win7, VS2013, Update 3. I tried to create a Xamarin.Forms projects in VS2013 and the Windows Phone project would not load. Error message is something along the lines of "cannot load project because Windows Phone SDK V8.0 is not installed".
Since I have VS2013, Update 3, I have Windows Phone SDK 8.1 installed (installed by default with my version of VS). I downloaded Windows Phone SDK V8.0 and tried to install it, but it would not install because you need to be on a Win 8 box to install that version of the SDK.
So it appears the creating a complete Xamarin.Forms project (IOS, Android, Windows Phone) is not possible in a Win7 environment. Can someone confirm this? Or am I missing something?