WordPress uses no conflict mode for jQuery but not when you use a cdn link to load jquery file.
You should use it something like this:
add_action( 'wp_enqueue_scripts', 'load_custom_jquery');
function load_custom_jquery(){
wp_enqueue_script( 'custom_admin_jquery', get_stylesheet_directory_uri().'/js/flexslider.js', 'jquery' );
}
Just that much is enough. No other registering, deregistering will be required. This code will load your custom-jquery.
In wp_enqueue_script last parameter is jquery. which ensures that before loading custom-jquery load jQuery file (available in wordpress installation). That’s the non conflicting mode. It is advisable that one should use this way only. Otherwise you might get conflicts with default jQuery file.
One more thing that you should consider while writing your jQuery code in custom_jquery.js is Aliasing the jQuery Namespace and use:
jQuery( document ).ready(function( $ ) {
// Code using $ as usual goes here.
});
in place of
$( document ).ready(function() {
//CODE
});
References :
jQuery Ready Aliasing the jQuery Namespace SECTION