in my Silverlight Windows Phone 7/8 projects I always used these methods/classes to get informations about the user phone:
Microsoft.Phone.Info.DeviceStatus.DeviceFirmwareVersion;
System.Environment.OSVersion.Version;
Microsoft.Phone.Info.DeviceStatus.DeviceName;
Microsoft.Phone.Info.DeviceStatus.DeviceManufacturer;
But now in Windows Phone 8.1 runtime they are missing. Are there some alternatives? My app doesn't use networking. Thanks and sorry for bad english.