demo rewrite.php

function otff_add_rewrite() {
    $url     = home_url();
    $page_id = 542;
    if ( $page_id > 0 ) {
        $link = str_replace( $url, '', get_permalink( $page_id ) );
        $link = trim( $link, '/' );

        add_rewrite_rule( "$link/([^/]+)/page/?([0-9]{1,})/?$", 'index.php?page_id=' . $page_id . '&demo_rw=$matches[1]&paged=$matches[2]', 'top' );
        add_rewrite_rule( "$link/([^/]+)/?$", 'index.php?page_id=' . $page_id . '&demo_rw=$matches[1]', 'top' );
    }

    add_rewrite_tag( '%demo_rw%', '([^/]+)' );

}
add_action( 'init', 'otff_add_rewrite' );

                    $rw = get_query_var('demo_rw');
                    var_dump($rw);
                    $a = $_GET['demo'];
                    var_dump($a);
                    die;