>2. Why would you even need to bother? If you legitimately open the door by mechanically unlocking >the door lock the alarm should not go off.
On most "modern" cars (15 years +) which are designed to be used with a remote key fob for unlocking, the alarm will be activated if you use the mechanical key to unlock the doors. To silence the alarm you then have to insert a registered/paired key into the ignition switch pdq.
It actually makes sound logical design sense, as a mechanical brute force on the lock, or a forged key will trigger the alarm.