We only provide patches for version 1.9.4.5 of Magento 1. This is the latest version and any older versions won’t be supported. If you run a Magento 1 shop in an older version, but have always patched it, it is likely that our patches will work there, but we cannot guarantee this. We only test our patches for version 1.9.4.5.
We test all our patches under PHP versions 7.2, 7.3 and 7.4.
Older PHP versions like PHP 5.6 are not supported, because they are not supported by PHP itself.