Demobbed.
A military discharge cant be removed from your record
No
Choose not to re-enlist (honorable discharge), bad conduct discharge, hardship discharge, medical discharge, die.
Dishonourable discharge
No. If you commit a crime as a civilian after you've been separated from the military, it has no impact on your discharge. Not that it really matters - you get convicted for a capital crime, no discharge is going to better your life after prison, assuming you eventually get paroled.
Probably not.
No. They would receive whatever discharge papers the Australian military gave them upon their discharge from service.
Walt Disney did not receive a dishonorable discharge because he never served in the military.
Look at your DD-214.
Yes, you can join the military with an uncharacterized discharge. An uncharacterized discharge typically means that your service ended before your commanding officer made a final determination on your discharge characterization. However, it is ultimately up to the individual military branch to determine if they will accept your application. It is recommended to consult with a military recruiter for more specific information based on your circumstances.
A girlfriend can not get a military discharge for her boyfriend just because he wants out of the army. He should talk to his superiors and find out if there is anything he can do to get an early release from the Army.
(for the US military) The U.S. Court of Military Appeals. See link below: