Pass php variables with WordPress pages

Hello.

Please I need some help.

I need to pass variables on WordPress pages as follows:

sitename.com/demo/variables1/
sitename.com/demo/variables1/variables2/

Using a particular page template, view: variables1 and variables2

In practice, I have to pass the pages slug (variable 1 and 2) when I use the given page template.

I tried with the code I put down below but it does not work. This code passes any variation instead of passing the variant only when the variant page1 and / or variant2 actually exist. If page does not exist, it give up error 404.

functions.php

add_action( 'init', 'isw_add_rules' );
function isw_add_rules()
{
add_rewrite_rule(
    '^demo/([^/]*)/([^/]*)/?',
    'index.php?page_id=12112&autore=$matches[1]&titolo=$matches[2]',
    'top');
add_rewrite_tag('%autore%','([^&]+)');
add_rewrite_tag('%titolo%','([^&]+)');
//flush_rewrite_rules();
}

template.php

<?php 
$autore = get_query_var( 'autore' );
$titolo = get_query_var( 'titolo' );
echo  $titolo . '</br>';
echo  $autore;
?>

Many thanks in advance.