Role of evidence in registered will

Once will is registered it cannot be challenged on the ground of signature. But will can be revoked any time during the life of the testator/executor.

Registered WILL is not easily set aside atleast on counts of authenticity..

The testator and witnesses sign in presence fo Registering Authortiy ( Tehsildar)....

means dy. registrar ?
like to know dy. registrar of which section/divn. has authority to verify and justify the will document ?