Hi!
VCAA has a prescribed text list (with contains many types of texts across many genres, from plays to novels to films to poems...etc). This text list changes every few years.
Schools choose a couple of texts from this list for each type of assessment (i.e. one for text response SAC, one for comparative, etc).
Essentially, not everyone in Victoria reads the same texts, it varies from school to school. However, all these texts come from VCAA's text list.
The exam structure is as follows:
Section A: A Text Response essay responding to one text (studied during the year at school)
Section B: A comparative essay comparing two texts (studied during the year at school)
Section C: A language analysis essay anaylysing language an argument use in an article(s) set by VCAA. This is unseen.
Hope this helps! Let me know if you have any other questions.