Hello There,
Thanks for updating in! When editing in Cornerstone, you can make use of the screen option to see how the content will look like in smaller screens. Please check this out: http://prntscr.com/g22229
Drag and drop should be working in Cornerstone. Can you confirm that you are fully updated? (Theme and Plugins)
Our latest versions are:
X Theme: 5.1.1
Cornerstone: 2.0.6
You can find the latest version numbers here: (http://theme.co/changelog/) Then you can compare them to what’s installed on your site.
If you find anything to be out of date, you can review our update guide.
Please let us know how it goes.