Property issues

My father age 69 yes is a retired govt employee and my mother got expired 8 years back. He is having 6 acres agri land owned by him and 4 acres got from his late brother as his brother does not have any children... he also have one own house and one house which he got it from joint property. Actually we are staying in Mumbai and he stays in my village along with his brothers... now he is showing interest in second marriage and also told that he will give one acre of agri land and one house...I came to know that the women have one child from her first marriage... 4 years back he also wrote one will saying that it’s his first and last will all the property will be give to me after his death. Now my question are :- 1. Will his second wife be entitle for pension after his death 2. Who will be the legal hire after his death if he doesn’t write any will 3. Can he cancel the will which wrote before and give all the property to his second wife including 04 acres which got from his brother and one joint property house. 4. What can I do to hold back the properties.... excluding the one acre land and one house as my father promised her...