OK, I will attempt to answer your questions as best I understand them:
1. A person who has never been in Australia cannot ordinarily incur demerit points on their drivers license.
2. The demerit points system administered in Australia does not ordinarily count demerits earned in overseas jurisdictions, so any points on an overseas license should not apply to an Austral***** *****cense.
3. Demerit points incurred on an international license whilst in Australia will apply to a local state license once you apply, and if in excess of 13 will prevent you from obtaining a local license whilst any suspension of the international license is current. How long a suspension lasts will depend on how many demerit points you actually accumulated, see the attached table:
Though it is also possible longer suspension periods may apply if the offence that exceeded the limit was one which triggers an automatic suspension period, such as high range speeding.
Good luck and I trust the above assists.
PLEASE RATE MY ANSWER.