You can safely delete all instances of ACF from the plugins page (it wont delete any of your field data or meta values). But take a backup first just for good measure.
Then reinstall the latest version of ACF and you should be good to go.
To me it would seem that someone has made manual changes to the ACF core files and changed the version number to avoid getting new updates. A very bad practice which I admit I’ve been guilty of myself earlier in my WP usage.
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