I'd like a plugin to change the URL of /wp-admin area for security purposes
There should be no options for this plugin (no database changes). The new admin URL will just be /admin-secret
When activated, if someone were to try to visit /wp-admin, they should be redirected to the 404 page.
If writing to the .htaccess file please do so using register_activation_hook(), and then have the code removed on register_deactivation_hook()
You would work locally on your own instance and then transfer the plugin to me afterward (you wouldn't be working directly on my server).