Main detail is the main point of your paragraph/essay. you want to be able to start and finish with that so it will remain within the reader thought for longer.
(We Brits have a saying "if a piece of literacy is stuck in your head, the writer has accomplished his or her goal" )
the supporting details are smaller points that correlate and support the main point. note that you should never start with a supporting point, nor should you ever end with one, it is simply there to extend and highlight the main detail. starting or ending with supporting details will ensure that the reader will almost instantaneously forget your essay and they may even find it boring because it doesn't show consistency.
Simile. In the sentence "Shining like a cascade of brown waters" It compared her hair to water and used the word "like"
C and B. A past tense refers to the past. Crawls is currently doing, was crawling could be either present or past, so if you have a multiple choice that would be one of them. C is crawled, meaning he was. And D is will crawl, meaning the future.
The subordinate clause is "unprotected animals got swept out" and the main clause is because "when waves rush in". hope u get it right ;)