No ... cows can't survive underwater, and the octopus can't graze on land ...
No.
Yes, cows mate with bulls to reproduce. Bulls are the male cattle that mate with the female cows to produce offspring. This mating process is essential for the continuation of the cattle population.
No, not usually.
it is called serving
Yes they do because all cows are girls and all bulls are boys
Cows can breed for as long as they are productive, which can range from one to 15 years or more.
if they didnt they would be extinct by now
It could be octopuses or octopi
It's a way of producing offspring and to pass one's genes on to the next generation. Cows don't live forever (nor do any animal on this planet), so it's crucial to mate to have other offspring pass on their genes to the next generation.
Cows will show signs of heat cycle (they will bellow, they will mount or stand for mounting), the bull will smell that she is in heat (often the cow will urinate and the bull will smell the urine-this is referred to as the Phleaman response). They will then breed.
It could be for defense, mating. or camouflage
Not quite; they have to give birth to a calf in order to lactate.