Section 12 - for cancelling the marriage

consult a good lawyer specialised in family law and File a petetion before the time runs as the petetion shall be presented before one yea from the discovery of the fraud.later ask the wife to contest and admit the fraud and settele the matter amicably.

Even if it is on mutual consent, do we have to provide the proof of fraud being done?

There is no mutual consent for annulment  u/s 12 of hma.

You may write in the  MCD petititon that the fraud played by the spouse and on the agreed terms you are going for divorce. But the MCD  is totally different from the nullity as in nullity there exists no marriage and in MCD parties are divorced.

You have not posted the complete facts.