Most linux distros have both of them installed. Can be called via python2 or python3. Or you could just set up virtual environments per project with the correct Python version.
For some reason, the bullets are showing as menu items rather than the actual menu in the example. I am properly missing something fairly easy but can’t seem to figure out what the problem is. I haven’t deviated from the example at all. Also, I have never had any problems with any JQuery code in the past.