Is Received Power and RSSI same thing? I have been looking into it and think they are the same. But please guide me the difference between them if they are not the same.
No it is not, RSSI only gives an indication of the received power. If you would have a large interfering signal on the same channel or an adjacent channel your RSSI value would be high yet the Received Power of the wanted signal would be low.
For proper receiver power measurements you will need a power meter or a spectrum analyzer.