At that point there wouldn’t be a way to prevent the post from being submitted.
Your only real option is to create an acf/validate_value https://www.advancedcustomfields.com/resources/acf-validate_value/ filters for the fields and do your own validation to make sure the values will be acceptable to where you are submitting them to.
If there isn’t a way to know this ahead of time it would be extremely difficult.
