What are the rights that son have when it comes to Property ??

Sir, i have many question regarding property sharing i will ask u point by point. 1.can my grandparents give all their property to my father's sister who is divorcee with no children ? 2. my grandparents has 2 sons n one daughter they made a will which contain our home is transfer or gifted (i am not sure) in the name of my father's sister can all this possible without my father signature? 3.can my father claim their share to court against my grand parents WILL because of this inequality? 4.divorcee with no children women can get the pension after death of her parents?? 5. If a legal WILL is written and registered, then will property be shared according to the will & wish of the owner of the property only?? 6.the owner of the property can gift their property in the name of his daughter only without taking affidavit from their sons that they dont know about execution of WILL in daughter favor?? n what if the one sons of the property owner sign or okay with the will in daughter favor can they execution of WILL in daughter favor without intimation of the other son who lives in the same house??