The property left intestate by your father shall devolve equally on all his legal heirs, therefore all of you three brothers and your mother shall be entitled to 1/4th share each in the property.
Now o your questions:
1. Do we have to travel to Pune to fill and sign relinquish deed ?
The relinquishment deed executed jointly by all other heirs in favor of one of the heirs is to be registered before the registrar's office within the jurisdiction where the property situates.
2. Can we sign the relinquish deed in Punjab also so that we don't have to travel. If yes, what is the procedure.
No, you have sign the registered deed where the property is situated.
3. Since mother has already transferred plot on his name which he registered. Do she also need to execute a relinquish deed ?
Your mother cannot the entire property on your brother's name, because she has no rights to transfer the entire property, she has marketable title and interest only to the extent of 1/4th her share in the property.
4. Once we sign relinquish deed , can we claim any part of property OR can it be voided forever ?
You will lose all your rights or interests in the property once you execute a registered release deed relinquishing your rights in the property.
5. What is the approximately fee to execute a relinquish deed.
In Maharashtra there is no stamp duty for transfer of properties within blood relatives. You have to bear Rs. 500/- towards the registration charges.
6. The cost of the plot is Rs 55 lakh
7. What forms , affidavits shall be filled to relinquish deed ?
Consult a local document writer who will take care of all the requisite formalities in this regard.
8. Can he execute his part of relinquish deed ( for some other property ) in our favor from abroad and will that be valid ?
He cannot do so from abroad, he can give POA to anyone who will be able to execute the same on his behalf in India.