I just did the 3/4 last year... without the 1/2 - and I found it ok..... It's not 'extremely difficult' - but can be challenging at times. Lots of memorisation is involved - and developing formulaic responses (with key words) to questions is the only way to do well.
Make sure you do lots of 'exam type questions', mark your own work - and make sure to 'tick all the boxes'. (We used the edrolo textbook in y12 - which helped a lot with this). You will also need to get your head around 'key science skills' - including knowing the definitions of 'accuracy/precision/etc...' off by heart - and being able to find the IV/DV/Controlled Variables etc... as well as ways to improve experiments.
My number 1 tip for all subjects (in y12); is Never - ever - take notes directly from the teacher's slides. Always take if from the textbook first - and then add anything extra they may have included. Teachers tend to either leave stuff out, or make mistakes.... So the best way to learn the content is to use the textbook.
Make sure to work ahead - and practice under timed conditions. This is where a lot of people struggle....
I suggest flashcards - and printing off diagrams/etc... and sticking them around your room. I also would highly recommend getting ahead during the holidays... and throughout the year. (Try and finish the course early)
Douchy's Biology podcast can be great too! I think he's just uploaded a new one for the current study design! Highly recommend his work.
Ummmm.... Yeah! Good luck with what you choose 🙂 Hope nxt year goes well 4 u!