The clues in the name, 2-20, so 20 zones max.
That can be a rf portal on the panel, 12 hard wired or wire free, or add a rio/ power rio giving 20 hard wired zones, or 20 rf zones.
If the cable is cut it will either tamper the house alarm if unset, or if the system is set it will trigger the bells.
You could keep the panel separate in the garage, get a relay to follow the bell, then strap a galaxy rf wired door contact to it, then say prog that as 24hrs at the house, call it garage, then it will SMS you that the garage has triggered.