Upgrade Safari on old iPad
My dad has an old iPad (circa 2013 I think) which won't allow an upgrade to iOS version later than iOS 9.3.5. He is getting errors from some apps saying that his version of Safari is too old. Is he safe to upgrade Safari to the latest version, despite being on an old iOS version? Is there any risk that the latest versions of Safari are incompatible with the older versions of iOS?
Thanks
iPad (3rd gen) Wi-Fi