Related to will

According to succession he is eligible for a share, if your father wishes to settle or convey his  property rights favg.you by WILL or gift deed or settlement deed,  he may not get any thing. Till such time he is eligible.

Hema , yes if the will is done in favour of your brother by your grandmother then your brother is the sole owner of the property, second if your father makes his registered will and wants to give his property to your brother then he will be the sole owner of that property also, but if your father demise without making any will then the property will divide in between you ,your two siblings and your mother it means the property will equally divide in four parts and you all get 1/4 share each from the property.

Yes..your brother is sole owner as per will and he has share in fathers property.

As of now, your brother, if the Will executed in his favor has been acted upon, shall be the absolute owner of the property he inherited through the operation of the said Will.  As far as your father's self acquired property, he is still the owner of the same, he can dispose it in any manner and to anyone during his lifetime and nobody can question his action.  However, if your father's property becomes intestate, your brother shall have an equal right of share in the property as other legal heirs and this has got nothing to with his acquisition of your grandmother's property through the Will.