1) on your husband demise your mother in law , you and daughter are legal heirs
2) your mother in law can execute release deed to relinquish her one third share in property
3) you need to obtain letters of administration from district court for immovable properties
4) succession certificate is only for movable debts and securities
5) LHC would not suffice
5) for sale of minor share in property you need court consent
6) after you obtain letters of administration then apply for mutation of property on your name and that of daughter
7) for formation of society contact local lawyer . After flats are sold then you have to form society