Usually the first to second week of methods is just revision of Unit 1/2 work, especially the functions. The Binomial expansion is a relatively new concept that isn't in Unit 1/2; however, if you do the set work, you'll be fine. Sometimes teachers choose which questions you need to do, but if you feel that you don't understand it too well, try extra questions from that exercise and ask the teacher or VN for help.
Most students (in my class last year, anyway) found Methods 1/2 too hard: too many new topics crammed into a too short space of time. Half of them dropped out of it this year. However, i can tell you that 3/4 is just an extension of 1/2; a few new topics, but mostly it is just taking topics learnt in 1/2 to a slightly harder level.
I basically already did Methods 3/4 through tutoring already, so right now in class i am consolidating my understanding. What i recommend is to try be a few exercises ahead of class - that way, you can have time to ask teachers which questions you are having trouble with and help other students (teaching others actually makes you realise whether you know your stuff or not). More importantly, because of the busy Yr 12 timeline with SACs here and there, keeping ahead actually gives you more time to revise key concepts for those SACs whilst everyone else is still learning the course.
(Btw, i bet i know why you thought Further wasn't your thing: the first few weeks are always dedicated to the Core, which has to do with univariate and bivariate data. I hated that too! With a passion! I refused to do any work on it.

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