Well, the thing with the Melbourne model is that they only offer general degrees: Science, Biomed, Commerce, Arts etc then you do postgraduate courses like honours/masters/MD/JD etc
If you want to do actuarial studies then you do Commerce and take the actuarial studies major. If at the end of first year you you decide to change majors, then you can easily transfer to Finance/Eco. You don't miss out on any prerequisite units if you want to take this pathway, although the only thing is you would now be doing the math stream for the quantitative requirements for the commerce course. That is, instead of doing QM1 and another quantitative unit in 2nd year, you would be doing 2 math units in 1st year and another 2 in 2nd year - you do these as breadth units too. It would only be a problem if you plan to do Accounting/Finance with accreditation since the pathway for that is pretty restricted, you would have to do extra units to satisfy the accreditation prerequisites I think.
Transferring is when you want to change from a Commerce degree to say Science. If you choose to do this then you can transfer internally at Melbourne or transfer out of Melbourne into another course at another university. It depends on the course, you can get some or all of your units credited so you wouldn't have to start from scratch.