Remove all removed pages from wordpress

You must use wp_delete_post() with second parameter set to true. The post will be completely deleted, not trashed.

// Use $args to get the pages you created previously
// See https://developer.wordpress.org/reference/functions/get_pages/
$pages = get_pages( $args );

if( $pages ) {
    foreach( $pages as $page ) {
        wp_delete_post( $page->ID, true );
    }
}

After that, you can use wp_insert_post() to create a new post with a slug previously used.

It may worth to consider to update the post instead of delete and create a new one.