Even a field that allows code to be entered will not run that code. It is something you need to build. To run PHP code that is stored in a field you would need to use PHP eval() https://www.php.net/manual/en/function.eval.php to run the code in the script. This would need to be done using an acf/format_value filter. https://www.advancedcustomfields.com/resources/acf-format_value/. This is considered unsafe.
To alter a message field to show a value from another page you could create an acf/prepare_field filter for the message field and you can get the value and alter the message.
