Translation:Have you been to Australia?
Sure, but literal translations chinese<—>english dont often work out very well. Just ask google translate. It should accept any translation with the same meaning.
去过 means already been/traveled to. This infers that "before" is implicit.
Not quite. Because "Have you been to X" is ambiguous in English. You might ask somebody who just arrived where they've been. And you might also be asking whether they have the experience of visiting X. To clearly permit only the second meaning you can say "Have you ever been to X" or "Have you been to X before" or "Have you ever been to X before".
All four should be accepted.