A friend of mine who owns a basic Karbonn A91 mobile phone came to me asked to reset his phone because he lost is password and there is no way to recover it. I have never used Karbonn phone in past and I have no idea how to reset it because his phone is locked. Can anyone tell me way to reset the phone , method or process for this brand.

It is easy, I don't have Karbonn A91, but have similar phone. All you need is to press and HOLD (VOL +) and (Power) button together for 5-10 seconds then then it will show Android Sign with red exclamation mark. Now again press power button to get stock recovery choices.

Please confirm if it works for you too.