This is the sample POA and it does need a photograph.
Here is how you have to get PoA attested by the Indian embassy.
The attested POA needs to be registered in India before it can be used to buy or sell the property.
Sealed envelope
There is no such requirement for a sealed envelope. The government officer in India makes up their own rules to harass and extract bribes.
So, it’s better you do what they say. You will need to pay a bribe anyway at some point in time though, anyway.
Address of property on the POA
I strongly suggest writing the address of the property on the POA and make it specific to the property.
Sale transactions should be done using the special power of attorney which means that you should write as many details as possible about the property on the PoA.