3. Your mother, if desirous of transferring her share of property both on her name and the inheritance from her deceased husband, she can do so either by executing a 'hibanama' or a registered gift settlement deed as per Transfer of property act.
4. The sisters, if willing to give away their share in the proeprty to their brothers without paying stamp duty, they can transfer the same by executing hibanama in respect of their shares in the property.
However they cannot mention the consideration received towards this hibanama.
If you want to mention the passing of consideration amount towards the relinquishment of their rights in the proeprty, then it would be advisable that they execute a registered release deed, which would attract very less stamp duty, i.e., 1% of the value of their share in the property.
5. In that case you can adopt the measures suggested above.