Air Conditioning

My mom says if you leave your cars air conditioning on when you turn the car off, so it automatically is on when you turn your car on, that it hurts the engine. Is that true or is she full of BS? It sounds like complete.

We have a small airconditioner, its the kind that is in apartments in the wall. I was wondering, is it good to use it even if the inside is cool and the outside is even colder? Also are air conditioner is making wierd sounds now, out side it sounds like popcorn is poping. Is that rare but normal or os that bad? If it is bad, is it from it being used in the cold? It is a modern airconditioner.

We have a small airconditioner, its the kind that is in apartments in the wall. I was wondering, is it good to use it even if the inside is cool and the outside is even colder? Also are air conditioner is making wierd sounds now, out side it sounds like popcorn is poping. Is that rare but normal or os that bad? If it is bad, is it from it being used in the cold? It is a modern airconditioner.