Accept and enrol in UNSW, and then if you get an offer in the Late Round, withdraw from UNSW.
You don't want to "defer" though. That's a completely other term that means "put it off for a while and come back to it later".
PSYC1021 is probably a Semester 2 course.
As for 24/6 UoC it stands for Units of Credit. Each Level 1 course is usually 6 UoC.
When they say 24 UoC free electives, they mean essentially 4 courses that you have to do.
Stage 1 is usually your first year (which would make sense because...
I just checked the handbook for b act/b econ and it totally answers the questions you're asking! Specifically the courses you have to do and the codes for them! What are you looking at.
You have not received an offer in the Main Round for undergraduate study in 2013.
Oh well, can't say I'm surprised not having an atar and relying on 2 units of undergraduate study. Am waiting on some prep programs.