Q1. why will the case of "Probate of WILL" may take 15 years to settle ?
This is incorrect and misguidance. The probate case may not take such a long time.
Q2 .In case, Mr. A files suit for recovery of possession / eviction of tenant, will it also includes declaration by the court that the WILL made in 2013 is not legitimate and the WILL made in 2016 is Genuine ?
If A is not in possession, he can approach the civil court seeking possession.
He has to concentrate on his probate case only, he should not unnecessarily involve himself in any other related issues.
Q3. In case, Mr. A files suit for recovery of possession / eviction of tenant, approximately, how much time will it take to finalise the suit ?
It may take atleast two years.
Q4. In case, Mr. A files suit for recovery of possession / eviction of tenant and WINS, does it also have the same impact as of "Probate of WILL" for all future circumstances and have absolute and clear title to property OR Mr. A still require to file for Probate of WILL separately ?
Yes.
Q5. Is it better for Mr. A to counter defense Mr. B that testator made the WILL under duress in 2013 and do not produce the medical certificate from doctor made in 2013 OR Mr. A shall also claim that testator was of unsound mind while making WILL in 2013 ?
It is not necessary, let the other party prove his case.