If you want to get information about a field that’s not created yet for a particular post, then you need to use get_field_object() using the field key.
The load_field filter can be used to get the information when a field is loaded https://www.advancedcustomfields.com/resources/acfload_field/
ACF will never rename a field key once it’s create. Unless Elliot decides to completely rework everything about the way ACF works.
