Hey there! Congrats on the 85%. Nice work; you seem set to do really well in the 'real thing'

I completed ITM in my 2022 HSC with a mark of 99 and ranked first in course. My advice would be to look at the syllabus itself. Ideally, your teacher will provide you with a summary sheet of 'what you need to know'. ITM is a bulky subject and this ensures you know what the exam might cover. Skim through the content points and identify areas that you don't feel as confident with, and target those ('classic study style' if you will).
For the multiple-choice section, it helps if you have a foundational knowledge of multimodal tech (like you know that a JPG, PNG, and AVIF are image files); if you don't, then no worries. Try making flashcards to get these quick facts memorised or maybe watch interesting videos about multimedia concepts while you eat lunch-- YouTube is full of these. You can learn a lot just from watching a Photoshop tutorial.
For the written responses, absolutely complete past papers. If your teacher's happy to do so, ask that they mark them for you. It can be a good idea to redo your past graded tests and perfect your responses so you gain a good understanding of what it actually is that makes the difference between a Band 5 and 6. Also, access catholic trial papers to broaden your scope of practise papers. If your teacher is reluctant to mark your practise papers for whatever reason, then mark them yourself. Focus on the 'learning verbs' (describe, explain, analyse, etc.) and dissect what they actually mean (do a Google search for 'learning verbs NSW', and you'll get clear definitions for them all).
Your major project goes a long way to achieving a Band 6. I've noticed that animations tend to receive better marks. I think this is due to the level of skill and diversity of techniques they require -- so if that's something you're considering, I would 100% say go for it. Don't neglect your major project portfolio. My animation was rather ordinary, but I put a lot of effort into justifying every single step in my portfolio. The longer and more detailed the portfolio, the better (mine was like 77 pages and ~20,000 words to give you an idea).
I hope some of this advice proves useful

Let me know if you would like any clarification or advice on something else ITM