Yes. Haven't you noticed that your hair gets oily. Your skin needs it as well, to keep it from cracking. Your hair is part of the skin, so it get oily, too.
Yes. One characteristic unique to mammals is mammary glands. They are glands that secrete milk.
Milk.
OIL
Yes, the feeding nipples secrete 'colostrum'
sebum
to secrete sweat and oil
Yes, but in mammals it is a minor function. (In salt water fish it is their major function.)
Woodchucks, ferrets, skunks, beavers, dogs, and cats are mammals who secrete a musky odor when frightened.
No. Mammals are defined as "a warm-blooded vertebrate animal of a class that is distinguished by the possession of hair or fur, females that secrete milk for the nourishment of the young, and (typically) the birth of live young".
This covers all placental mammals and marsupials.
Endocrine glands are glands which secrete oil, sweat, enzymes into ducts. Example: sweat glands, sebaceous glands, digestive gland, mucous. Correction! Exocrine glands are those which secrete to the outside (can still be inside the body- for example hormones involved in digestion) which have ducts and secrete oil- sebaceous glands. Endocrine glands secrete to hormones the "inside" and DO NOT have ducts, they are ductless.
Spiders have an oil they secrete to keep them from sticking to their webs.