1. What are the most difficult topics in methods 1 and 2?
For me, it was probability. It's vastly different than it is in Units 3/4, and you actually have to think hard for 1/2 probability
2. On a scale of ten (10 very hard), how would you rate methods 1 and 2 in terms of difficulty?
4-5/10, units 3 and 4 even less. 1/2 was harder than 3/4.
3. Any advice, tips or tricks or things to be aware of?
If you want to do well in Maths, you MUST know the concepts like the back of your hand. If you see a question, you should be able to instantly link it to concepts and the relevant formulas or concepts should pop up immediately. This is the most underlooked part of Maths in general I believe, and it is why people don't hit raw 40s. You also must be incredibly efficient with your usage of your CAS, so know where certain functions are, the menu, etc, etc.
4. What would you think of doing methods 1 and 2 in year 9 (i am not, but ik others are)?
Pointless. Once you get to Year 11 or 12, you'll most likely have forgotten the topics unless you constantly revise. For me, I also find it easier to do some subjects when I'm older (think its a maturity thing),so probably more beneficial to do 1/2 in Year 11. Unless the people you know are absolute geniuses on the road to get 99.95, then uhh, yes