Colostrum from the mothers teats.
Milk.
milk
Yes, mammals care for their young.
All mammals suckle their young. That is one of the defining characteristics that makes them mammals. Even egg-laying mammals (monotremes which include the platypus and echidna) suckle their young.
No, milk is not an alloy. An alloy is a mixture of metals, while milk is a liquid secretion produced by mammals for feeding their young.
The only animals that suckle are mammals, but not all mammals give live birth (the monotremes do not). So the answer to your question is "non-monotreme mammals," but there is no common official term for them.
Yes. Kangaroos are marsupials, which are a sub-group of mammals. All mammals suckle their young.
Mammals give birth to their young for purposes of procreation. This is what ensures that the life cycle of the mammals is continued.
Your question seems to suggest that mammals that feed milk to their young are a subset of mammals. But all mammals feed milk to their young. That, along with the presence of hair, is the defining characteristic of all mammals, without exceptions.
Vertebrates with hair, giving birth to live young, and that suckle their young are mammals.
Yes, they are mammals. All mammals, except the platypus, have live young.
Mammals feed their young by suckling until they can accept solid food.