Since the questions are pretty broad, just practise with pieces you find online. Since it can be from Year 11 topics as well, you can look up classical (baroque, romantic etc.) pieces AND last 25 years. And then just apply them to the questions in the past papers.
E.g. "How does the composer create interest through the use of tone colour etc."
Then, practise melodic dictation the same way, just get a short sample of a work.
Then get the pieces you've studied in class into short summary mind maps or whatever format you like. Then practise question 4 (even if you don't have an unseen work to practise with because you'll know how to analyse from the first step in this post).
Also, most teachers should have CDs from past papers, if not you should ask. Also remember that teachers have trials (where they will have to have the audio files).
Seeing you're in year 11 (if the HSC year is right) you probably haven't done past papers in class yet.
Tbh, I was stressing about the paper a lot more in year 11, but when you get to year 12 you find it's the easiest bit (because of all the practise you'll do throughout the year). If you want to start worrying about anything now, just look into what Last 25 years music is, do some listenings and write things down for them (just things you notice about WHAT makes Last 25 years music different.
Then date it and make into a diary entry so you can already have a head start on your composition portfolio.
Imo, composition is the most stressful part about Music 2, unless you're a natural talent.