Ooo, so close, yet so far...
Cobber means a mate buddy or friend. Like with you I might say, g'day cobber or would you like another beer cobber?
So...g'day is pronounced more... without the good part. Sort of G....Day. Not Gee day...G-Day* So, you were close...I'll give you one more question to answer and if you get this right you can come in...
Is Australia an island, a continent, or both?
Both! That's easy.
You're in...GTG! Just show this at customs and say, g'day cobber, G-dog says I could come.
You'll breeze right through and they'll give you a free starter pack including a beer, some Vegemite, Tim Tams and some chicken salt.