multiple apps on apache server

I am developing a PHP web application and did deploy it on Apache web Server port 80, However I need to deploy the old version of the application again for testing purpose. I would like to deploy the old version on the same web server with minimal configuration to it. the first app already deployed under /var/www/html I would like to deploy the old version under /var/www/old on port 81 for example

how this can be done ? do I need to make changes to Apache configuration or create new Virtual Hosts ?

Regards,