There might be plug-ins installed but never used. What’s up with that?

Thanks for the screen recording.So, to know for sure if the website is using ACF is any way will be to check the theme code for any occurrences of the following functions:

• get_field()
• get_sub_field()
• the_field()
• the_sub_field()
• have_rows()

These are the most common ACF functions used to output ACF data in a theme. For a full list, please see our docs:https://www.advancedcustomfields.com/resources/You can then also search your theme for an occurrences of the string "acf". Our actions and filters will include this namespace, as well as some of our functions like acf_add_options_page().If your theme isn't making any reference to ACF functions/filters/actions, and there are not field groups created, it would be very safe to say that ACF / ACF PRO is not required on the site :)Also, it's worth noting that no data is deleted / modified when deactivating / reactivating the ACF plugins. So there is really no risk with disabling the plugin - except if your theme is expecting the plugin to exist, which may lead to a PHP error.