I support Saji,s views in this regard. You may be working, at any location, in the world. Logically, since you are employee of Indian Company, you are governed by the rules as stated in your Appointment letter, especially about Resignation, Notice period, Leave matters, etc. Other situational things, like office timings, holidays, medical assistance, travel assistance, other work related rules/laws, can be under Australian rules.
I have a strong doubts about statements made by Anonymous, especially in the matters of Resignation. If the foreign company, which is presumed to be collaborator of Indian company, has issued its own Service rules, to an Indian departed employee, then the statements of Anonymous become true. A person joined an Organisation in India, anywhere he goes in the world, for work, on deputation, he will send his resignation to his Original employer.
There are many foreigners come to India, for working in the offices of their Indian collaborators, I don’t think, if he wishes to resign, he is governed by Indian office rules. He will send his resignation to his US Office.
Anyway, these are my personal thoughts. I fully accept and appreciate, The best and only answer, given by Anonymous, “Talk directly to the HR in Australia”, for which he himself has provided references. Great job !!