The HSC isn't a piece of art it's about judging your ability to write normally, eroticism is not good unless jusified and even then considered a no no.
Swearing is allowed but not if you use it generously. The bigger problem with this is that I'm yet to come across a swear word that isn't colloquial. Yes Fuck is common, but it's still colloquial.
And think of it this way, how do they tell you apart from a literature genius who can get into character extremely well and a douche bag who doesn't know any better?
Keep those things in mind and don't read any Warren Ellis before going into your exam.