1. If i understand the question, you can use the word "direito" with several meanings. Like in english. You can use to show a direction or position (right side; turn to the right); you can use it to say that something was done correctly. Besides that, here, the graduation to became a lawyer is called DIREITO.
2. Gostar and curtir are almost the same thing. In some context, GOSTAR could be used to say about something that you care about and CURTIR is a word more informal. But in general you can use both.
3. TU is used mostly for people from south of Brazil. Santa Catarina and Rio Grande do Sul states.
4. Sometimes used for the same thing, but VIVER is more general, i mean, you can live (viver) in many ways, but MORAR is when you want to talk where do you live, the place.
5. Yes. When someone tells you "Não dá", mean that something can not be done.
6. Didnt understand the question.
7. When you have a doult (Dúvida) you probably will do a question (pergunta). They are diferente, but they could both be used as nouns.
8. Dizer and falar almost the same, yes!