1) No, ACF does not export of print PDF files. Is there a custom field plugin that does?
2) I’m not sure what you mean. The admin of ACF works pretty much the same way in the pro version as in the free version. You can test the free version here https://wordpress.org/plugins/advanced-custom-fields/ and you can see what the admin of the flex field looks like here https://www.advancedcustomfields.com/resources/flexible-content/. If you’re talking about the front end of the site, ACF does not create anything on the front of the site, this is up to the developer to do. Again, try out the free version and read the documentation here.
3) Yes, ACF does not do anything with custom post types and you can add field to any post type that is created in WP by whatever means you choose to create them.
