It is my understanding that the "admin user" in CRM online does not work just like OnPremise. The "Restricted Access Mode" is only available if you add it to the form, but an error is raised if an attempt is made to set the "Restricted Access Mode." The blog post link provided in the prior post is applicable for non-interactive users (those not accessing the screens).
In CRM Online a license is required for every user that needs to access the user interface, regardless of whether they just administering the application.