You're asking for a lot of information. Also, schools like it when you know something about them before you contact them.
So it would be better for you to go to the websites of the universities you're interested in. You'll find answers to most of your questions there.
You could also just write to request their catalogs. You'll receive big packages that answer most of your questions.
Find out if they have special offices or associations for foreign students. Then you can direct some of your questions there.
Once you've done that, if you still have questions, phone or write them.
Also, I wouldn't use "Dear Mr./Mrs." If you don't have a name, say: "Dear Registrar" or "Dear University of Tazmania."
Student or Learner