Alarm.com ADC-SWV100 Smart Water Valve

Does ADC-SWV100 link directly to my 2GIG-SP1-GC3 panel? I currently have 8, 2GIG water sensors positioned throughout the house and they are working fine with the 2GIG system. In fact, they already detected two leaks and sent me an alarm before the water did any damage. Now it is time to add the auto shut-off!

Partially, yes. The Z-wave connection from the water valve connects to the Z-wave card in your panel, however, the automation controls and enrollement are handled through Alarm.com. We're not familiar with 2GIG though, so there may be some control you gain directly through the panel, but primarily the valve shutoff will be in response to Alarm.com noticing a water alert has been triggered. 

Alarm.com ADC-SWV100 Smart Water Valve: Is the system programed to periodically cycle the valve to ensure the ball value remains working?

Yes, once per day the SMV100 will run a 15 second "valve check" where it will close and open the valve to make sure it's free of restrictions. 

My water pipe is 3/4 inch. Is this device compatible?

The ADC-SWV100 is a 1 inch valve, so with some modification to your current pipe you could make it work for shutting of your water flow. However, I would not recommend using the ADC-SWM150 with the included water flow meters as your smaller pipe may throw off the readings of the sensors.