Apps can be developed using Visual Studio 2015 (Community edition can be downloaded for free).
Apps can be written using languages such as C# or Visual Basic with XAML, JavaScript with HTML, or C++ with DirectX and/or Extensible Application Markup Language (XAML)
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.