1) Can we i.e. I, my mother and sisters demand partition of ancestral property even our father is alive?
Your mother has n rights in your ancestral properties especially when your father is alive. Even you can claim a share out of your father's share only and not from the entire property. In fact your grandfather's property shall not become ancestral property.
2) How much share of said property we get?
Out of your father's share, assuming you have two sisters, you may get 1/4th of your father's share in the ancestral property
3) How much land can father sale?
He can sell his own share of property
4) As there is no partition of this ancestral property between father and his brothers, no fixation of boundaries done in coparcenars till today,if my father sell part of this ancestral property 2 hectors out of these 9 hectors to third person with mentioning boundaries as E- Remaining of said property , can transferee claim right on purchased specific & perticular land?
Without proper partition, it cannot be ascertained that whose property is what, hence the sale deed shall be invalid if there arises a property dispute including a partition suit.