DevKinsta allows you to use every PHP version that Kinsta supports and more. This allows you to test your site with older PHP versions in DevKinsta. The available PHP versions in DevKinsta are:
Changing PHP version
Navigate to the Site configurations screen (wrench icon) for the site where you want to change the PHP version. Under PHP Extensions, click on the PHP Version number and choose the version you want from the dropdown list. The site will be inaccessible for a short period of time. Once the update is complete, your environment will be up and running with the new version.