For the engineering complementary studies electives, do the levels of your electives have to match the year you take (or are meant to take) them in, or does the level of the elective not matter? For example, if I need to take one elective in Year 2, does it necessarily have to be a level 2 course, or can it be any level?

level doesn't matter as long as they are in the elective list. I am going to fourth year and I took a level 2 Econ this summer.