Last year I applied for my in laws. I try to answer your questions based on that experience. Just bare in mind that it was not their first visit to Australia.
1. IMMI Account
2. It was not required.
3. It was granted for 3 years.
4. I'm not sure about this one. I showed their bank statements as well as ours.
5. It was not required.
6. It was not required.
7. After applying I received an email from the embassy, asking for insurance if I want them to issue a 3 year visa. I arranged the insurance, email back the paperwork.
Hope it helps.