Questions about Ring Alarm System

Hi. I would like to buy 5-piece kit Ring Alarm System, but before use I need to know couple things.  1. How sensitive is the motion sensor? I have a cat and I am curious if the alarm will be armed, cat can trigger the alarm? 2. If I do not arm the alarm and leave the apartment, will I receive a notification from Door sensor if someone will enter to the apartment?  3. Is it possible to volume down the siren due to the presence of the cat in apartment?  4. I am going to add the ring Stick Up Cam to this system in battery mode. How it will work? It will start record the video only when someone try to open the Door and trigger the alarm?  Thank to all for reply and help.