If you are aiming on iOS and Android with Windows Phone 7/8 as a plus you should use C# as the language and Xamarin Studio as the IDE/Framework. You may also choose to use Visual Studio on Windows as an option. Take a look on their website: http://www.xamarin.com Even Microsoft is using Xamar...
Cross-platform frameworks are just now becoming robust and stable enough to be a real concern. The most popular frameworks include React Native, Xamarin, and Ionic. The trade-offs are typically speed of development vs. flexibility and complexity. If you use a lot of platform-specific integrations...