I am traveling to Australia soon. I am on the ETA and want to potentially extend my stay to six months. I was wondering, while in Australia of course, if I should apply for the extension of a tourist visa first and THEN have my booking adjusted (because I have round trip tickets) or if I should adjust my booking first and THEN apply for the visa.

Also, I may have posted this in the wrong forum, I wasn't sure where to post it.

No one knows who's read this, yet? It's important because I know Australia is very strict with visa overstayers so I don't want to adjust my booking, get denied the visa extension and then become an overstayer by accident, but I don't know if I need the itinerary first before I can apply for the visa extension. I am well aware ETA cannot be extended, but I know (as per the Australian government website) that I can apply for a tourist visa extension to stay longer. I would've just applied for the regular tourist visa first, but this trip was sort of sprung on us at the last possible moment so I don't have time to apply.

I am visiting in the first place because my wife is a citizen there and has to return soon and I was going there to visit for part of the time while her visa for permanent residence here was processing.

First, AFAIK, your ETA is only valid for THREE months. You need to apply at an Australian Consulate for a Tourist visa (Subclass 676) <link>, which can allow you up to 3, 6 or 12 months' stay. You can apply from within or from outside the country, but IMO I'd rather arrive with the visa safely stamped in my passport - YMMV, of course, and some tourists can apply online. (Google can be a better and speedier friend than waiting for a reply on FlyerTalk... Australia visitor visa resolves quickly to Visa Options - Tourists - Visitors - Visas & Immigration .

Be aware - an ETA can cancel a visa - I have had it happen, and when I arrived at BNE the saving grace was the officer who basically handled it ("I have a mate in ACT [Canberrra, the capital,] who will handle it" - and he did, but it's not something to rely on).

According to their website, you should submit "a plane ticket (if you have one) detailing your departure
dates" with your visa application.

I would think that you should get the visa first, and then change your flight. However, if the ticket cost is going up, then do that first.