Hello Big-Al,
Thanks for reaching out to the Community! You would be please to know that you can see who is logged on and using the system, message them and even log them out. All you have to do is enable this feature. In multi-user mode, the QuickBooks Messenger icon is located in your system tray at the bottom-right of your screen. The messenger automatically starts whenever you are logged in. To launch this, simply double-click the icon.
I am attaching this article detailing this feature and more about QuickBooks Messanger.
To answer your second question, yes, it would. All users would need to be on the same update as the server.
Please let me know if you need further assistance! I will be happy to help!