(a) Yes. Somewhat surprisingly, the colonies only became 'states' as part of the process of forming the federation known as the Commonwealth of Australia.

Essentially, the colonies simply continued their separate existence, but were now described as states. Each state retained the power to govern within their own borders, with responsibility for a wide range of matters.

But, by joining in the new federation, they also agreed to give specified powers to a new federal Australian government which would have responsibility for matters of national importance throughout the whole of the Commonwealth.