Perhaps, You may remember the fact that the Japanese Empire invaded Australia during World War II.

They didn't get very far. Got a bit stuck along the way. though a couple subs were destroyed in Sydney harbour I think.

By agricultural countries, do you mean they just grow stuff? I am not sure that is the case since the 50s for either Australia or Finland. Finland definitely not now, since the paper industry is much smaller, but the tech industry is large.

Perhaps, From the perspective of powerful Asian empires such as Japan and China, Australia will be understood as a Finnish-level country with weak self-defense.

Perhaps. But Australia also hosts the early-warning missile system for the US, so if it would come at a heavy price for whoever attacked it, as it would draw the US immediately into battle. And, Australia does have a professional army, so they could likely hold their own for a little while.

In Finland, there is a small professional army, but pretty much all men are trained. Also, if the attack came into Finland, it would be seen as a move against the "true" West, so would draw others into battle from Europe at least. It would be WWIII once the border was crossed.