mono&diglycerides

Question

I read that they can come from both animal and vegetable derivatives. Everytime i called a company it was from vegetable. Is it always kosher even if it is from an animal? 2)how come shabbat is over 45 min after sunset. I though the latest tzet is 35 min. at the US naval observatory web site they have the time for the end of twilight which ranges (in NY) from about 28-32 minutes after sunset. Is that useful information? (http://www.usno.navy.mil/) 3)on may 13 you mentioned that one can ignore the lights triggered by motion. I am trying to understand why. Is it a psik resha dla nicha leh d'oraita? but then i thought the halacha is that it is asur. which step did I err in? 4)a front door or a window to a house has a bypass switch so as not to trigger the alarm when opening the door. can one flick theswitch on shabbat. Nothing actually happens other than the current goes directly through the switch box instead of going through the window contact.