On the occasions that I have travelled with travel insurance, (other than medical insurance), and I rented a car, they just asked to photo copy the policy, as proof of insurance. But I never did it long time ahead.
I would check with the RACV or your own club. They should have all that information.
If you are booking through a consolidator, they may take care of all that.
A rental company cannot rent a car uninsured. All compulsory insurance will be charged. As for all the extras, I have never worried about them. To me it is worth taking the risk. The worst that can happen is you cause an accident, you have to pay. But the personal injury to all parties should be covered under the normal compulsory insurance.
Police will check a rental cars' insurance if there is a reason to pull you over, so the company would not let you take a car without that..
Where my situation has always been different. I do not book a car long beforehand long before hand. Sometimes just a few days before.... and more often than not, I have been upgraded without cost.. When I don't have travel insurance, I just tell them I only want to pay for that which is compulsory. Then again, I have never rented for longer than four weeks.
Others may have more information, but this has been my experience.
Lifey