In Australia, Australian National Flag Day is celebrated on 3 September. It commemorates the day in 1901 on which the Australian National Flag was first flown. On that day Prime Minister Edmund Barton announced the winners of a competition to design a flag for Australia. A large flag, 5.5 by , was flown over the dome of the Royal Exhibition Building in Melbourne.

Based on the paragraph above can we conclude that "Australia did not have its own flag on Sept 3, 1900"?
Yes