Yes, although you should carefully watch to make sure the puppies aren't being smothered or crushed. The mother will lay over her puppies when they are newborn to keep them warm.
No, the puppies will open their eyes on their own in 7-10 days.
She probably isn't biting them. It is more like she is nipping them. This is normal. This usually occurs as a sign of discipline when the puppies are being rough. The mother dog will tolerate the puppies, but she will control her young when they nurse to hard.
Eating is normal for your pregnant dog. The puppies will get their nutrition from the milk which is supplied by the mother's nutrients.
She could still have a retained puppy. How is she acting sick?
Yes, mother dogs do love their puppies, and will become upset if a puppy dies.
Because the puppies get cold.
the number of puppies a dog will have depends on the breed, and size of mother dog in question.
The mother might die unless the puppies are surgically removed.
My bichon frise's mother had my dog at 2 years old, so bichon frise's can have puppies at 2 years old :-)
the other puppies will be born and the dead puppy will simply just come out.
You see the puppies around the mother.
It depends on the breed