Essentially your obligation is to give honest full and frank answers to any question asked by an insurer. They might ask you whether you have committed any offences over the past 5 years. The question may or may not refer to demerit points. Whatever the question is, give your best answer, and if you do not know the answer, then don't give an answer.
So if the question is "Any demerit points" (highly unlikely question!) then the answer is "yes" because these points will stay with you for the rest of your life.
The insurers will check your driving record after you make a claim and then they will determine whether or not you lied in your application for insurance.
If you have accidents that you do not tell them about, you put your insurance cover at risk. They simply won't pay out if they think you have mislead them.
I noticed that some insurers, if you tell them about not-at-fault accidents, will still give you rating 1, but will quote a higher premium than if you do not tell them about those accidents!
So people who have never had an accident are charged a higher premium than those who have had accidents? That is nonsense.