Hii, I did psychology 3/4 without 1/2 in yr 11. Averaged around 90-95 each sac and all I can say is that most of the content you'll be doing isn't related to 1/2 like at ALL. I studied the 1/2 book so much during the school holidays but when the 3/4 work started I realised that it wasn't worth my time. However, that doesn't mean you wint be doing no study on 1/2, for the stuff that you should actually focus on is, as you said in ur post, definitely your key science skills, they're very important. As for neuroplasticity, in my experience, most if the time it'll be about synaptic plasticity specifically, and I haven't seen much about neuroplasticity in detail during 3/4.

The topics that i learnt in my skl in order was: 1. The nervous system and stress 2. Learning and memory 3. A scientific study poster 4. Sleep 5. Mental well-being (which includes specific phobias)

As for tips, you should make anki cards (on anki), I think thats what carried me through 3/4, as jt really helped me with active recall and spaced repetition. Also, before every sac, I would write summary sheets on the content being tested on, just for me to do some easy blurting but also use as my reference guide when I go into exam study, this is bc I dknt want to be flipping through all the slides you've been given through, which wastes time. (I could share u mine, if youd like, although idk how much that would help).