as far as Karnataka is concerned only local lawyer can guide you as to when registration was made mandatory in Karnataka for POA for sale of property
2) POA for sale of property needs to be regsitered The Registration (Maharashtra Amendment) Act, 2010 effective from 1 April 2013 has resulted in amendment of Section 17 of Registration Act, 1908 I (Act) in sub-section 1 in its application to the State of Maharashtra. As per the said amendment, an Irrevocable Power Attorney relating to transfer of immovable property in any way executed on and after the commencement of Registration (Maharashtra Amendment) Act, 2010 shall be compulsorily registered
3) Unregistered Power of Attorney for sale of immovable property shall not be capable of being put into use and shall not affect any immovable property comprised therein. It shall not be received in evidence of any transaction affecting such property.