Yes they do and if the kitten is born with an ailment the mother cat can sense it and will most likely kill and eat the kitten The same is true with dogs.
Most definately, a mother of any sort, will know, they sniff, lick and try to move the cat/dog, if there is no movement or the animal is very sluggish, they will cry.
Yes she does (my cat had kittens yesturday and left one to die becuse it was sick)