Unfortunately I don't think smart gates are currently installed at Terminal 1 arrivals according to Dubai Airports.

If they are installed, yes, there is a separate queue for non-registered smart gate users, so after you go through the gate you will be validated at a desk and then you can use it on your next visit to DXB.

On departure, you'll need to go to a desk.

I think Marhaba offer a paid for fast track service at T1 if you really want to skip queues though