a) The Aussies said that before they lost the Ashes and were being cocky. If you think beating England isn't their number priority, you're wrong.
b) Of course the subcontinent presents different challenges. But there's no reason why to be best in the world, or second best in the world, you need to win in India. If Australia beat everyone away except India, they'll still be the best team in the world. Unless India, or someone, is beating everyone away. Your point is a bit of a nonsense.
c) Of course England will be trying in the series, but it isn't top priority, just as is it isn't India's top priority. But it is a more important series for India because a) you're at home; and b) you've just lost to your arch rivals.