Sheep, not sheeps. It’s one of those weird English words that doesn’t take a ‘s’ when plural.
Technically, yes-ish. Wool is a winter undercoat which, in primitive sheep, is shed in spring. Most modern sheep have been bred to not shed their wool, although the genes do still exist in commercial breeds and one can often see sheep looking a bit ragged at this time of year, with clumps of wool coming away from their summer coat.
Not all sheep grow wool, and other members of the Caprinae family, such as Cashmere and Angora goats, do. Indeed, the undercoat of Angora goats, mohair, is so routinely sold as ‘wool’ – particularly in suits – that there’s no point in differentiating it now.
Confusingly, Angora rabbits, source of Angora fibre, not only have the name of the goat that does produce wool which is called mohair, but were originally known as wooled rabbits. (It’s also possible to spin Angora cat hair, but enough already).
So, there’s no reason why the undercoat of other animals cannot be called wool, too. However, in practice, these other fibres tend to take the name of the animal it comes from: alpaca, llama, guanaco, vicuna, camel, yak, bison, chinchilla, mink, possum. And finally, qivuit, from the musk-ox.
But if the fibre is from a plant, like cotton or linen, or is synthetic such as nylon or polyester, it is NOT wool, and I will get very sharp with you if you call it wool.