Can a MOU be accepted as a will

My father and mother had decided to execute a will jointly in connection to all of their movable and immovable assets. They had decided to give a fixed amount to my sister from movable assests and 50% from the sale proceeds of residence. The responsibility of execution of the same was placed on my shoulder. Unfortunately, before preparing the same in written form, he took his last breadth. After his demise my mother to honour his last wish as well as for the sake of future clarity executed a notarised document in the shape of MOU keeping me and my sister as party. I have heard that for executing transactions there are 3 possible ways as per law. 1. Will & Probate 2. Succession Certificate/Letter of Administration 3. Legal heir certificate. It is also said that except the Will & probate the rest process are time consuming, tedious and complex. I would like to know whether the said MOU can be placed in the court to accept the same as will. Any other suggestion is also wlcomne.