Deregister Stock jQuery and Load Custom jQuery on Specific Pages/Posts

loadCustomjQuery.php

<?php

// WordPress 5.6 comes with a very recent version of jQuery and it's not suggested to use an older one.

if (!function_exists('load_custom_jquery')) {
    function load_custom_jquery() {
        if (is_page(array('page-slug-one', 'page-slug-two'))) { // Replace 'page-slug-one', 'page-slug-two' etc with your own page slug
            wp_dequeue_script('jquery');
            wp_deregister_script('jquery');

            wp_register_script('custom-jquery', 'YOUR_CUSTOM_JQUERY_URL_OR_PATH_HERE', false, 'X.X.X', 'true'); // Replace 'YOUR_CUSTOM_JQUERY_URL_OR_PATH_HERE' with actual path and 'X.X.X' with the version of that jQuery
            wp_enqueue_script('custom-jquery');
        }
    }
}
add_action('wp_enqueue_scripts', 'load_custom_jquery');