Man that's impressive you're going for the competitive entry pathway!! Good luck!!No, I took some other pathways through my 20s, so never finished an undergrad. I'm here working my way through HSFY to apply via general entry to make it into med.
Re: HSFY - it's a pretty crazy year. As we are on different entry paths, my experience won't be quite the same as what you will face, but there will certainly be some parallels. I think the main thing that I've seen the Alt entry students struggle with this year is the twin challenge of the course material and family situations for those with young families. To help with the course material, there are a number of prep-courses available from the Uni including the physics course mentioned by Stuart above. There is an equivalent chemistry course also, I believe. There are also many in-semester aids available like drop-in times, additional tutorials etc. The good thing about the Jumpstart course is that a number of mature students take it, so it's a good chance to meet others in the same boat. Having one to three other like minded individuals to form a study group with is hugely rewarding and provides an invaluable group to bounce ideas off, and to use as a first port of call. Don't be afraid of engaging with the youngsters as well. 50% of my study group are school leavers from last year, and they're absolutely awesome. They have been crushing the assessments so are an integral part of the group. It's a good deal as I get to tell them about the 90s and noughties, and provide advice on life! It's a good trade haha. I think finding out the main resources that are available should be a priority prior to starting the semester, and then ensuring you use them as a matter of course, rather than just before a test. There are a number of excellent tutors that are available that many students use that can definitely be worth the typical cost of $30-$50 per hour. But all in all, just remember the required standard, and work to that. I think many of the Alt students are quite nervous until the first assessments and then once they achieve to the required standard, a lot of stress goes off.
For external commitments (ie family) it best to ensure you treat your HSFY as your primary focus for the year. Depending on individual knowledge and efficiency, in order to achieve the required grades for Alternative entry, a 40 hour working week is more than sufficient. Also as Stuart has said above, focussing on learning techniques should be your main task prior to commencing studies to ensure your learning is efficient. I did quite a reasonable deep dive into available literature about what the main tools for learning and over all, they are quite simple. Active recall, spaced learning, and practicing the test, are really all you need to succeed. How you do that is entirely up to you, but I have becoming a big advocate of a programme called Anki which does spaced repetition and active recall all in one programme. There are other ways this can be achieved, but I firmly believe it is the most efficient 'high yield' method. I'm achieving a grade that should be sufficient for med, and have yet to own, or read a single or the textbooks or assigned readings for the year. Finding high yield stuff and focussing on that is the best way to ensure you can really focus on study, but make sure there is enough time available for you have a life outside of Uni.
I guess that's a short overview - happy to answer anything more specific.