This is most likely not a CMake error (the error indicates that CMake fails to build a simple test project with v140 toolset). If you install Visual Studio versions out of order (VS2017 first then VS2015) then it may corrupt the installation and uninstalling both and reinstalling in VS2015, VS2017 order might fix it. Were you be able to build a project with v140 without CMake as I described above?
Yes. Slicer runs in your browser with full GUI.
There is Slicer image with GUI available via web browser but it’s quite old; and there are the regularly updated images but I don’t think any of them is configured to show the GUI in the browser.
@jcfr @pieper Is there a docker image of recent version of Slicer that has web-accessible GUI configured?