People studied in year 10? wot
Year 7-10 means very little in your performance in senior years, my year coordinator said if i continued how i was in year 10 i would get a 70 atar (trololol), now i'm on track for MUCH better.
Just apply yourself in year 11 from the start, don't think it doesn't matter because it does. It is the foundation for year 12, you learn your most efficient ways to study, gain experience in how to answer specific types of questions etc. I think 2 hours would be adequate normally, with more obviously for exam periods. Try and focus to work on consistency, 2 hours a day is much better than 5 hours for a few weeks.