Poa registered when resident indian, now oci, validity?

Dear Sir,

My brother registered a general power of attorney to my father to do all acts including purchase / sale of immovable assets, maintain accounts, obtain loans, etc. in 2007, when he is resident indian. He has mentioned that he is going to London, for the convenience he is registering this deed. In 2013 or 2014 he has taken British citizenship. He his holding 2 flats and land in andhra pradesh. Now he want to gift them to me.

2007 registered POA is still valid or not? Is my father still be able to register gift deed with old POA.

Please do suggest way and clarify.

Thanks in advance.