Regarding the asterisks:
The free demo version only displays full info for a limited number of devices.
Devices beyond the free demo limit are shown with asterisks. This limitation is removed when you
purchase and enter the licence key.
Regarding the blocking:
WiFi Guard is a purely monitoring solution, so it cannot block or manage other devices. This is not because WiFi Guard is lacking the necessary functionality, but simply because it is technically impossible to block a device directly from an application. No other software similar to WiFi Guard can do it. Please see
this article for details on what you can do.