To grant or restrict permissions for authenticated and anonymous users or other user roles, settings must be configured in CMS.
Admin may allow user registration from CiviMobile app by checking the related box in CMS in Account settings.
ACL permissions distribution is required to control user access to CiviCRM data. When ACL permissions are distributed, an admin will control the operations (access/create/view/add/edit/delete/disable) certain users (authenticated user, anonymous user, administrator, etc) will perform on a specific set of data (Contacts, Activities, Cases, Activities in cases, Events, Participants, Relationships, Memberships, Contributions etc.)
For example, anonymous users can view only their contacts, while administrator will view any contact in the CiviCRM database, export contact info and perform activities such as send email, phone call, etc.
To verify that appropriate permissions have been set in CiviCRM, go to the Permissions page.