Can you apply? Yes, of course, provided the course you want to enter is offered as a mid year entry. Not all are. Check UAC.
I think what you meant to ask is "how will they judge my application".
USyd consider previous tertiary history of at least 1 year FTE. If you have only had 1 semester at UNSW they will not consider it. Judging from your post, I suspect you only just started uni this year and did the HSC last year. In which case they would only use your ATAR,
PS - suggest the mods delete all the off topic posts within this thread.