I am playing around on ForeFlight and saw some non towered airports near or under B or C with clearance deliveries phone number (19N). 1. If I am VFR departing do I need to contact the number for clearance? 2. Can I call them on the ground for Class B clearance and also request flight following? 3. What about towered airport (KLNS) with a phone number for clearance delivery, for VFR departure do I need to contact the number?