Yes. It only takes one tie.
I would say no because once their pregnant they don't go into heat
Once a female dog goes into heat they are able to get pregnant.
"They" who? A dog? A cat? Please include this information in your question.
Yes
Once or twice a month should be enought.
A dog must be in heat to get pregnant. Heat is basically her ovulation cycle.
No. A pregnant heifer will rarely come into heat, and her heat period will only be once or twice during her pregnancy, then stop until after she has her calf. But she will not go into heat and start to lactate at the same time she's bred. She can only either be pregnant and have a small chance of coming into heat, or be pregnant and start to lactate (which only happens when she is nearing the end of her pregnancy).
Because her hormone level is very high. Once she becomes pregnant, her hormones change, and her body recognizes this, so she is no longer in heat.
A female cat will typically stop being in heat once she successfully mates and becomes pregnant. If she does not mate, she will continue to cycle in and out of heat until she does. If she does not become pregnant, she may experience a rest period before going into heat again.
False heats are rare in cows or heifers that are already bred. If a heifer does go into heat when pregnant, it only occurs once or twice and that's it. But normally, no, a heifer won't still mate when she's pregnant.
Every 28 days, unless of course she gets pregnant, then it's normally once a year.
No. Once a cow is pregnant she won't have any signs of heat again, until after she gives birth to her calf.