1. High altitudes have alternating daily extremes of climate that can start of from hot, burning days, to freezing nights. There is also results in rapid dehydration due to the strong winds and low humidity. A decrease in air pressure is also cause by high altitudes which can disturb homeostasis because of the decrease of oxygen that is being released through the vascular system. This is what causes many people to get sick and have a number of symptoms.
4. Personally, I don't think you can use race to understand the variation of the adaptions listed. I've always believed that race is nothing but physical appearance, that how I always viewed it. I don't think race has anything to do with connections especially on how you can adapt to high attitudes. There are cultures that live in high altitude areas but I think that's because they were born and raised in those areas. This is why the study of environmental influences on adaptions is a better way to understand human variation.