Owners harassment

This is more a personal issue and depends if any on such agreement in writing about such.  For harassment, we can not guide any thing.  If he has not given additional set, just reply him through registered post in wriing that duplicate set was not delivered at the time of giving possession and deny his allegations and ask him further not to disturb you with such calls / letters.  If owner has to repay the advance demand such advance refund within 15 days.  At this stage except denial, you have got no other option.  If there are really duplicate set, compensate it as it is fair demand and justified.

Gently ask him to replace the lock if he wants.

In future let the owner state in writign if another person has to come for handover and handover with list of items under proper acknowledgment.

Hi Vijaya,

 How did you occupy/possess the premises i.e., as tenant, co-owner, licenced or any other manner? Your eviction has been a court order or any other mode?

You should sincerely declare that you do not possess duplicate keys, if you do not have them, otherwise hand them over to the owner . Once the keys (possession) has been handed over you are expected to be away from the premises.

Is there any sort of dispute in instant fabricated situation to be opined and advised?

Addressing the experts should be respectful and not in a formal (friendly) manner as you have, mend yourself.