You should really start to do some research of your own...most of your questions can be answered by looking at uni/faculty websites/uac guide etc etc
However as a guide...around 50% of law graduates don't become lawyers. It is increasingly being seen as a more generalist degree.
That's a lot of people, doing a wide range of things, like - management consulting, investment bankers (if you combined with commerce), academia, politics, comedy (aka Chaser), doing whatever their first degree was but using law to give a heads up to employers that they are smart, work hard etc or just to give them a edge against people they are competing against for jobs.
Some people just don't end up using their law degree. It doesn't necessarily mean it was a waste of time, they have learnt how the law works, and may go back to it later in life. University can be about learning, not just about narrowing you into a profession immediately after graduating (although yes, granted, you've spent a lot of money getting there). Ditto for people becoming lawyers straight out of uni, then later down the track doing something else (further study, politics, consulting, banking, anything in the corporate world).
That said, I don't see the harm with starting out in a combined law degree (even if it was just because you got the marks), and then if you hate it, drop it. I did law because I got the marks, I hadn't even considered law before the uai came out (have had no dealings with law etc in the family - no ones a lawyer, or even in the business/corporate world). I decided that if I didn't like, i would drop it, and I surprised myself and liked it - turns out I might end up a lawyer. Of course, if you don't like it, or you know you don't like it, then don't do it.