1.Can we all challenge the will and request for its cancellation.
You can challenge the Will only when you feel that it was executed fraudulently or a fabricated document.
2.As the witness ( father of beneficiary of will ) along with executant's ie my father's identity documents used were cancelled at the time of usage, can it be a ground for filing a suit for misrepresentation of documents.
The documentary proof, if used for identity purpose only, then there is no grounds for challenging the veracity of the document.
3. In case another will after this has been prepared ( notarised) in my mother's name, can my mother still transfer this property and bank accounts in question to any one of us or any body else or it is compulsorily to be divided among all heirs as per Hindu Succession Act.
If the Will in dispute has been over taken by another will executed at a later date, then the the will prepared at a later date shall be held valid and on that basis, the beneficiary becomes the absolute owner of the property acquired through such a bequest. The beneficiary can dispose this property in any manner as per her desire to anyone of her choice, nobody can question this act.
First of all confirm that the original will written by your father has come into force or not.?
Whether there was any subsequent will executed by your father during his life time?
Whether there is a suspicion about the Will ?