1) how to get separate shares on sale ? she should gift shares in her undivided property to sons & grandsons OR do a partition deed. what taxes & duties are chargeable for transfer ?
You have stated that your mother want to sell her property and to give away the sale proceeds to her two sons and two grandchildren, then where is the question of partition or undivided share etc.? Your question is about partition or sale?, If it is her own property what prevents her from selling the property and dividing the sle consideration equally among the proposed beneficiaries?
2) If the proceeds from house property are invested by each individual fully into another house property then can they claim LTCG exemption ? If any individual has already two house properties in his name then can he still claim LTCG exemption after purchasing third one out of proceeds of sale ?
The LTCG exemption can be availed by the person who sold the property and not by the person who was gifted with the money. The sale proceeds or otherwise is a gift in the hands of the donee so there is no reason for the donee to claim exemption under LTCG, however your auditor w3ill be having a different reason to convert the same to enable you to claim the benefits, hence consult the auditor on this issue.
3) In what mode of property transfer the granddaughters have claim to grandmothers property ?
Grandmother's property is her own property hence she has full rights to transact with it in any manner of her choice and desire. She can sell it, stlle it or gift it or bequeath it to any person or persons of her choice, nobody can have right to claim even a single bit in it during her life time. Upon her intestate demise the property shall devolve on her own legal heirs and not on grandchildren, so the granddaughters do not have any right in it.
1) Can the gift deed specify amount of share, for each individual, in the house and the land(plot) over which it is built ?
Gift deed pertains to the movable property or to the immovable property? Whatever there is no rule to have any specifications in favoring any one person(s), it is the donor's will and wish to allocate accordingly.
2) My mothers property in discussion is not self earned. It is bought in her name by my father. So is gifting by her that property to sons and grandsons(excluding granddaughters) legal ?
Once a property is in the hands of a married woman, it becomes her own absolute property and she has full rights to do whatever she want to with it, there is no question of ancestral claim in it and the root of acquiring the said property cannot be questioned by anyone.