Yes accepting an offer will usually require you to enrol in the subjects for the first semester. However, you are still able to withdraw as normal
There are no fees if you withdraw from the course before the census date (end of March) as set by the commonwealth government (for HECS etc)
There are a certain number of places for courses, and perhaps not all of them are issued in Round 1. For example, the uni may set an enrolment cap of 200 students for something like Science but only get 150 preferences, therefore 50 remain for the other rounds (
hypothetical - I actually have no idea re: numbers).
As the rounds progress, the chances of an applicant receiving an offer for a specified course decreases. Majority of the course places are taken in round 1. Hence why it is important that everyone has a plan B, just incase
.
Thanks