Bachelor of Applied Geology

Anyone who started Geology in second semester might be able to help me out?
I’m trying to enrol in my second year (starting sem 2) but only 2 units are available as the other 2 require pre-requisites. I was advised I can do 2 optional units instead, but I’m a bit confused as to how these work and what that will mean for my remaining units in year 3? Will I do the other 2 then?

Or should I take 6 months off and then start my second year in sem 1 so everything is in order??