1) what are the content of SPA? does it authorise your brother to purchase property on your behalf and to appear before sub registrar for registration of sale deed .
2) if SPA is well drafted and authorises power of attorney holder you dont need GPA
3) Any power of attorney executed outside India needs authentication. So, any power of attorney executed outside India should be authenticated by a notary public of that country , the Indian consul, or by a representative of the Central Government. Such documents need to be stamped within three months from the date of receipt in India, to be payable at the district registrar's office.
The attestation of power of attorney is not compulsory . However, it is advisable to get the document attested by two witnesses.
4) registration has to be within sub registrar office where property is situated
5) Section 85 of the Indian Evidence Act applies to the documents authenticated by a notary. A court will presume that every document purporting to be a power of attorney, that has been executed before and authenticated by a notary public or any court, is properly executed and is a conclusive proof. Each page of a document notarised should bear the official stamp of the notary disclosing his registration number and jurisdiction , and also his signature. Appropriate notary stamp has to be affixed.