It may be too late for you but it might help someone else: basically what I’ve been told for QCE Methods is that everything builds upon itself. So if you’re doing unit 3 it may have stuff that you learnt in unit 1, same as all maths has times tables that you learnt in grade 3 or whatever. The externals won’t specifically ask questions about unit 1 or 2 content, but you may need to use a process or formula you learnt in yr 11 (units 1 and 2) to answer a more complicated question from unit 3 or 4.

Actual example: recently we did Unit 4 Topic 1: further differentiation and applications 3, which is about the second derivative so quite obviously you need to understand how to differentiate, which we learnt somewhere back in unit 1 or 2.

Hope that helps someone!