Forced Will prepared under duress & registered!

If the will is registered then there are less chances of forceful inducement upon the testator because the registration of document requires the person to be presented before judge and judge examines the testator with many questions and only then registers the document.

You can though challenge the will on many grounds and if the testator is alive you let her record the stamen for wrongful registration under inducement.

If the property belonged to Testator solely as her owned property then she ahs the right to give it to anyone she desires

1)      How to retrieve the copy of WILL?

If you know where the will was registered you can apply for certified copy of will in that court.

2)      What legal action can be taken in the matter.

You can challenge the will in the court to get it nullified

3) Persons involved are antisocial elements.

You have to produce witness to prove that in the court

The will comes into force after the death so convince to cancel will or challenge will after death of testator.

During the lifetime of testator will can't be challenged  on any ground .Testator has option to cancel the will or rewrite another will..Latest will shall prevail.Besides this effected party can challenge the will after death of testator on ground of coercion, pressure and undue influence .

If your mother is alive then the Will cannot be enforced by the beneficiaries.

Hence you can ask her to cancel the registered Will even by an unregistered document.

If you documentary evidences to prove that she was sedated and the Will was prepared under suspicious circumstances, a criminal complaint can be lodged.

But since your mother was present before registrar while registering the Will the chances to prosecute them is very bleak 

Yes.  I agree with the advice of the above expert Sri T.Kalaiselvan Sir.