2) Short term: One short-term adaptation to the stress of the cold is one that any reader can recall for themselves: shivering. In order to increase body heat and keep a person active, we start to shiver as a reaction to the cold. Shivering is the exact opposite of sweating, with the benefit being to warm up a person.
Facultative: One facultative adaptation to the cold is vasoconstriction, which is the narrowing of blood vessels as a response to a cold environment in order to retain body heat.
Developmental: One developmental adaptation to the cold, specifically exhibited in Mongolian people is having short appendages, which creates a smaller body area and makes it easier to retain heat.
Cultural: One cultural adaptation to the cold, again exemplified by the Mongolian people, is a nomadic lifestyle. Specifically, herders migrate along with their herds of livestock (horses, sheep, goats) across Mongolia to less extreme (in regard to the cold) locales so their herds can graze and do not freeze to death. Also, the people themselves are not tied down to a specific environment, so they can retreat from the advancing cold to a degree.
3) The benefits to studying humanity in regard to clines rather than other classifications are that they are less biased to the organizer's beliefs, more accurate, more holistic, and give a wider view to humanity that can be seen as a spectrum of adaptations for specific niches. The information we gather from these kinds of explorations is helpful because it paints an accurate portrayal of human evolution and adaptation, rather than lumping people into categories over trivial distinctions, such as race. This information can be used in a productive way by anthropologists to aid other groups of people who fall under the same niche. Adaptations one group has developed may be applicable to another group.
4) Race is not a strong enough breakdown/organizational system to explain the adaptations I expounded on in question #2. These adaptations aren't race specific, they are environment specific. Race is a weak organizational system for characterizing the human race. The adaption perspective is much more holistic and unbiased, focused rather on what is actually the case rather than socio-political organization based on power and privilege.