Answer:
1. The two boys talked about going somewhere for a drink.
2. They could be friends or colleagues. They are comfortable communicating with each other and they talked about being cooped up with work.
3. The underlined words in the dialogues are too informal and weird. We call them slang.
4. Casual (informal) language and Formal language.
5. The difference between the casual and formal language is that casual uses more inappropriate words since you mostly use this expression when you are communicating with your close friends and family. On the other hand, the formal language is mostly used when you are in a formal setting and it is important to mind your manners, especially during a business luncheon or meeting.