A:AnswerThe Ring Doorbell is for detecting activity outside. The keypad is for setting the alarm and the actual alarm box is for detecting the sensor activity. Yes you need the whole system .
A:AnswerYes you can change the settings for the individual sensors as to whether you want them to sense motion and go off on either armed and away or home and armed.
A:AnswerAs they are meant to be used inside, they will not hold up to the weather. Also, outside use would get a lot of activity due to birds and animals.
A:AnswerYes. You can customize the names of each door sensor. When the door is opened, you get a notification on the ring app to let you know which sensor was triggered.