The shortest way to find the main idea of a text is to look for a repeating idea or main event in each text. Sort of like looking for a repeating theme. If you're reading a story about how Jane went to a tiki bar and what she learned there, you'll probably see several main events reoccur. Such as she forgetting something or disregarding someone's feelings over and over again, leading to something bad happening to her. A Main Idea is usually stated in the first paragraph of the essay. Clear and out there.
I cant answer the other things for you, as it looks as if you'll have to look for the topic statement for each major paragraph. Usually the topic statement is the first sentence, or the main idea of each paragraph, most of the time clearly stated in the first sentence.
