With the PHP Raw widget, you can create everything you want.
There is no limit to what you can do, easily write the PHP code with an advanced code editor. You'll have access to all WP functions and data.
This widget has limited access only for Administrators, like WP native Theme Editor.
You don't need to use opening and closing PHP tags in this widget. Simply write the snippet and see the magic.
Return the ACF Field
echo get_field( "field_key" );
Check the Length of the String
You can use the String functions to manipulate the String values. For example, use
strlen() to return the character length of the String.