Hi.

The question is very simple: can the administrator (myself) set MyJspace to restrict the access to private users' pages just a very specific group of users?

The idea is the user to include whatever materials they want to be seen just for him/her and another kind of user within a Joomla! group.

Thanks.

You can set the access level page per page for a Joomla group.
For Joomla ACL usage, set ‘Access level using ACL’ = ‘yes’. You can set a default group for the new pages.
You can set it as administrator from the backend. The user can set it itself from the frontend (page admin panel)

Yes, but the problem is that there is a select box with three options in the front-end for the user to choose: lock, registered and public. I want it to show just lock and special-group. No public or registered. The contents are just for the owner and the users within the Special Group.

Is it possible to set that selector?

Yes, Like I wrote : set the option ‘Access level using ACL’ = ‘yes'.
And you will have the Joomla groups (you may have to clean the cache and refresh the page first).

Yes; now it shows the full listing of user groups, but the user shouldn't be able to offer access to any of them, but just to a single group.

Is there a way to limit the user group? I do not see such an option in the configuration. Perhaps editing the database?

The access level must have just two options: lock and a special group of users.

there is no option to restrict the list