You don't need mod 3 at all (only the very basics, but you can just revise them when you start mod 7). Mod 2 is important, but collisions don't show up. Mod 1 is very important (suvat is important for projectile). However, relative motion doesn't show up as well. Mod 4 is good to know, but you can do mod 6 entirely without doing mod 4 (that's what I did). Don't stress it, but forces and mod 1 suvat are important.