You should be able to change the PHP version without downloading an older version of WAMP. I haven't used it in a while (I've been using XAMPP lately) but I think you can right-click the WAMPP icon in the tray and click on the PHP folder. From there I think you can change/check the version.
EDIT: Here's a guide:
https://kostasbariotis.com/multiple-...on-wampserver/