Power of attorney for sale of property

Dear Friends, I need a legal advise on sale of my mother's property through Power of Attorney (POA). My mother has a property (flat/apartment) in Thane (Maharashtra). She wants to sell the property now. Currently, she stays with me in Bangalore, Karnataka. Since she has medical problems (Parkinsonism), she wants to perform the sale through her own brother residing in Navi mumbai (Vashi). My queries as follows: 1) Should she make a General POA or a specific POA in the name of her brother for conducting the sale & registration of the flat? 2) What is the rule & process in bangalore to issue a POA for her brother staying in mumbai, to conduct the sale of an immovable property on her behalf? I was told by one of the lawyer that her brother and herself has to be present in person physically in Bangalore to register the agreement copy and POA in sub-registrar's office. Please let me know if this is correct? 3) Should this POA done on Rs. 200 or Rs. 500 stamp paper? 4) What are the charges applicable (lawyer, stamp duty, registration, others if any) Regards, Mani