Xenko currently supports Windows, Android, iOS, Xbox One and Universal Windows Platforms (UWP). Xenko also supports most popular VR devices and has experimental support for Linux.
No. Xenko 3.x is covered by MIT license.
Xenko is open-source, highly modular, and super-versatile. You can use it to create mobile, PC and VR games, or as a high-end rendering engine for applications such as training simulations or architecture and engineering software.
Yes. You own all the content you make with Xenko.