to be a mammal they have to:
give birth to live young
have hair
be warm blooded
have mammary (milk) glands
Both. Humans are animals in the order Mammalia. All mammals are animals, but not all animals are mammals.
No, all sea animals are not mammals. Fishes are not mammals, but dolphins are mammals.
possums are BOTH! mammals ARE animals! all mammals, reptiles, and amphibians and so on are ALL animals.
Not all mammals have four legs. Bats are mammals, but have only two "legs." Whales and dolphins are mammals, but have no legs at all. What distinguishes mammals from other animals is not the number of legs, but the presence of sweat and milk glands.
Unless you exempt humans, who are mammals, yes. All mammals are animals. So are birds, snakes, fish, snails, worms and clams. Mammals are animals that are warm-blooded, breathe using lungs, have hair and fur, and mostly give birth to live young (monotremes are mammals that lay eggs).
yes because mammals are animals and humans are mammals so there for everything is a animal.
Not all animals, but most mammals do, hence why people have periods (people=mammals)
Mammary (milk-producing) glands are the primary distinction between mammals and other animals.
All mammals
I assume "non mammals" in your question means all animals that are not mammals. There are over one million species of animals in the world that are not mammals. We cannot give an exact number because we do not know how many undiscovered animals there are. Mammals make up less than one half of one percent of all animals. If you are asking, "How many individual animals are there on earth that are not mammals?" then no one can answer.
Guinea pigs are mammals. All animals with fur and give milk are mammals.
One of the defining characteristics that distinguishes animals from plants is that all animals feed either directly or indirectly on other living things.