Not sure you can do it with that hook as the hook will give you all the new data not a comparison between new and old. Can you explain exactly what it is you’re trying to achieve, there might be another way to achieve it.
Depending on the your implementation, you may use the acf_load hook to store the values in a variables and then in the pre_save compare the values
Not really, ACF is for custom fields!
Actually no! This is not resolved – I’m still having an issue!
Cancel that, it seems it was working just fine – I was unsetting the $args array after the ajax request
