Succession Certificate obtained even when there was a registered will

Hello My question is that my grandfather died making a handwritten registered WILL just 7 days prior to his death mentioning details of movable property namely FD's in his wills and those were bequeathed to some hypothetical trust. That trust has never been formed till date. Even that registered WILL seems to be suspiciously constructed as the attesting witness no.1 is my grandfather himself and there are a lot of handwriting differences also. Later on after his death, my grandmother immediately applied for Succession Certificate in District Court for grant of money and FD's of same account in name of my grandfather. She was well aware of that WILL but she herself concealed that registered WILLS Court granted her Succession Certificate also after all the necessary inquiry and publications. And she took out the money and used it for herself. I have these queries--- 1. Now, can that registered will is assumed to be just a forged document when the attesting witness no. --1 is himself the testator and there are a lot of handwriting differences ? 2. Or will it be assumed to just a fake piece of paper made for name-sake and which was never followed, has been set -aside as my grandmother obtained succession certificate for the same bank assets mentioned in my grandfathers will ?