Thank you so much for your detailed advise.
Just for the prices, I'll check the olx. I usually refrain to make any deal with any individual through telephone. Instead, I'll check availability of PTA non approved in local mobile markets with having good knowledge of the market, I could have better bargaining options.
Regarding the approved phones, which ones would you suggest. I am purchasing for my kid and basic purpose is to play games like PUBG with range from 15000 to 20000