I just thought sharing this info will be helpful to anyone...I came to Ausi on a tourist visa after 2 months submitting my partner visa application (I got a one year, multiple entries, 3 months maximum stay visa) I was supposed to go back since i was completing the 3 months by end of this month. As i did not have the 'no further stay ' condition on my visa i applied for an extension. Actually I had to apply for a new tourist visa to stay in Australia for another 6 months. I was granted it in 3 days.
I applied online and had to pay $340 (much cheaper than going up and down)
No supporting documents were required other than filling the online application. (There was one question asking why i need the extension where i had to explain the reason in one sentence. Other than that it was the same tourist visa application)