1. Is it legal that the selling the undivided property by my third brother's son in law without consent of other legal heirs? Is there any law or law section for that. Please mention the particular Section No.
Yes his act is illegal, he cannot sell others share, you may refer and peruse Hindu succession act.
2. Is the buyer (purchaser) of 1/5 th share land has any rights to demand the particular portion of land on his preference (area or location) to other four legal heirs?
No he cannot claim it that way, he can seek partition and division by good and bad soil .
3. Is other legal heirs has to allocate the particular portions of land to the buyer (purchaser) of 1/5 th share of undivided or unpartioned land?
This can be decided in the mutual partition also.
4. Otherwise for acquiring (with draw the land from buyer of 1/5th share of land) our land if we settled the amount of sale deed with interest amount as on date will be allowable?. Is court will allow to settle this payment through court to purchaser of 1/5th share land through court?
It depends on the pleadings and the mutual compromise agreement arrived between the parties.
6. Due to problem in EC no body will come forward to purchase balance 4/5 (major portion) of our land. What is solutions for this?.
There is no problem, you have to convince the buyers properly. Take the opinion of a lawyer and keep it in possession whenever there is a query in this regard.
7. We given many complaint against him in many police station. But no body take
proper action against him.
You may approach court with a private complaint under section 156(3) for relief, contact your advocate.
8. One of public prosecutor given the statement letter to police station that "My third brother's son in law sale of his 1/5th share is legal as per document he produced" Is it correct? If it is not correct what we would take the action against him.
The public prosecutor cannot give opinion about this civil matter, only a government pleader can give one. However nothing can prevent you from challenging this opinion before court of law.
In above matter. Who did the major mistake? Who will be benefited more ? How we have to solve the problem without file the case in court?
Without knowing the background details or facts, it will not be possible to give any concrete opinion.
10. Myself only facing the problem and fighting the opposite persons to solving the problems for three and half years but other three legal heirs not ready come and solve the problem. They want only final benefit of money after sell the land
You may fight only for your share and dont bother about their shares.