Just give her the proper feed according to what gestational period she's in, provide water and mineral and some shelter and let Nature do the rest. No need to pamper them with anything extra that they may want but won't need.
Anytime of the year.
AI is a method for a dairy cow to get pregnant. She should catch (or get bred) within a day or two after being AI'd.
A heavily pregnant cow, or a long-bred cow. Or, a cow that is expecting soon.
It shouldn't. Prolapses usually occur after a cow has given birth, not when she's still pregnant.
No, not usually. On rare occasions, a cow may experience false heats during pregnancy where she can be ridden by a bull, but otherwise, a cow that is pregnant stays pregnant and doesn't go into heat until a couple weeks after she's given birth.
A pregnant cow who gives birth is a mother.
It should only be a matter of a couple hours.
No, the cow will not go into estrus after she becomes pregnant.
Talk to your cow. If she is pregnant your character will mention how see and her baby is doing. If your character does not mention a baby then your cow is not pregnant.
Bred cow.
Antibiotics can cause abortions if not administered correctly or given at a time when the cow doesn't need it. It won't hurt the cow, no, but it may hurt the unborn fetus inside her.
Yes by law you will be held guilty, as the cow was yours you should have taken care to tie it well.