Since you do 2U I'd recommend you have access to the Cambridge 3U prelim book and do exercises for those topics since the questions can get quite hard at times
https://thsconline.github.io/s/yr11/Maths/
just do questions topic by topic
Also try doing some yr 12 2U past trial papers since prelim content is assessed in the HSC
Maths: Do practice and practice. There is no other substitute for maths other than practice. Also focus on what you're weak at and work from there. Practice questions in which you make lots of silly errors and practice questions you'd otherwise struggle to understand at times. Remember to ask...
Exactly
That's why you don't trust these fucking idiots and trolls on this forum who say "25% internal is 12.5% of the total HSC" when clearly it's fucking not
Just focus on what you're weak at: http://community.boredofstudies.org/1178/general-discussion-2017-hsc/359200/balancing-study-time.html#post7224726
In regards to studying what you know, I think it's best to just cram all that info when you're not focusing on your weak spots
This is one of the reason why you should help each other out during the HSC, so if you they do well, you will do well (as long as you have a decent rank)