Like I said, ACF uses an older version because some of the functionality from the old version has not been ported to the new version, and it’s functionality that many ACF users would likely be upset to loose. As far as updating ACF, you’d need to take that up with the developer by opening a support ticket, I’m sure that the developer can explain better than I can why he’s still using the old version.
https://support.advancedcustomfields.com/new-ticket/
