Yes.
Get it spayed. Spaying a dog means removing its eggs.
If the female is trying to get pregnant with a male dog then it will go on the males back but if the female dog is going on the males back while pregnant then it may means that they wanted to have another baby.
By mating with a male dog.
No
Sometimes.
doggy style. How did you think they do it?
Yes.
Often, a male dog is protective of the pregnant female dog, usually if he is the "mate." Sometimes dogs, mates of the pregnant dog or not, will act aggressivley towards the female dog, also known as the "bitch."
Yes but it has a better chance halfway through heat
She could die.
No