You can easily check which version of jQuery is loaded on a page (or whether it is loaded at all) by running either of these commands in your browser console.
jQuery().jquery jQuery.fn.jquery $().jquery $.fn.jquery
All four of these commands will return the same result. If jQuery is loaded successfully, you will recieve the version number, e.g
If jQuery is not loaded you will recieve a message along the lines of
ReferenceError: jQuery is not defined.