It's only good for the initial understanding of topics.
All the questions are at Q11-Q12 level. If you don't expose yourself to any other textbooks/past papers, you'll get a band 2.
Eh. The top kids will usually stay at the top, and the bottom kids almost always stay at the bottom. It's the middle kids that will move around, whether it's because they take year 12 more seriously and move up to the top, or because they don't care anymore so they fall to the bottom.
You're in year 9. Just chill. You might change your mind about what courses you want to do between now and getting your HSC.
I changed my uni preferences like 6 times during year 12.
They have to give an actual date for submission. If they just said "Week 3/4", then you have every right to hand it in on the friday of week 4. Definitely take it up with the principal or the board of studies.
It's all about the ranks. If the lowest mark in student A's cohort is 50 for the exam, student A will get 50 for their internal.
If someone in student B's cohort gets 100 in the exam, student B will get 100 for their internal.
You go to a small, low ranked school so it's hard to say, but I would say it's quite likely you would get over 90. The thing that could potentially wreck your ATAR is maths, so work on that for the HSC.