You can apply for a visa to visit Afghanistan through the embassy in Canberra
Not sure but I don't think they allow VOA.
You haven't mentioned the purpose of your visit to Afghanistan, but be aware that the Australian government recommends that you DO NOT TRAVEL there for any reason. This Do Not Travel warning has consequences for your travel insurance ie it is highly unlikely that you will be covered. Because of the lack of infrastructure, the high cost of providing a service , and the great danger to personnel who would be sent to assist you, insurers will very likely decline to offer any cover. You're going to have to rely on the kindness of military-attached medical services if, for example, you get ill or are injured, and they're not going to be happy to see you.
If you are going for work purposes or to volunteer, talk to your employer about the security arrangements they provide. about 6 years ago