What browsers can be supported? For example IE 11 or 9?
Any modern browser will be perfectly fine. For Internet Explorer, we recommend at least version 11. Appkit uses progressive enhancements so for older browsers the application will still work but in a feature limited fashion.
What is the process we must follow to accomplish responsive design?
As long as the existing templates are not compromised, responsive design will work out of the box. The user interface being adapted is a customization of a fully responsive template.