After receiving a lot of contradicting information, I decided to read all the related acts/AIR citations/judgements myself and clear all the myths.
1. Myth: There can't be more than one general power of attorney. Earlier POA has to be revoked before you appoint another
Wrong, you can appoint as many power agents (General or Specific) as you want. You are responsible for all their acts.
2. Myth:POA issued outside of India MUST be endorsed by the Indian Embassy.
Wrong again. POA signed by a Notary public of the country you reside is good enough (Notaries Act - Reciprocal arrangement between countries). However, this will have to be registered with the sub-registrar in India. There are tons of cases with arguements saying that POA notarized in the USA are not valid without an Indian Embassy attestation and each one of have them have been overruled.
Alternatively, you can have this POA endorsed by the Indian Embassy which is the same as registering with the sub-registrar. Courts will agree/presume that this document exists.
3. Myth: If you issue a new POA, it automatically cancels/revokes the old POA or you must revoke the previous one before issuing a fresh POA.
Wrong. You can appoint as many agents as you want (specific or general). The only problem is that a conflic may arise with these power agents contradicting each other or acting on their own. Let's say A makes B his power agent in addition to C who has been an agent for a while. C acts first to sell A's home to X. That transaction is good and A will not have any interest in the home any longer. If B, unaware of this transaction, sells the same home again to Y, A will be held responsible for the transaction. Y can now sue A to get his money back.
Hope this helps! I believe I have information to back these statements. Please feel free to contradict the same and we can enlighten each other.
PS: I'm an engineer and a business student. :)