Hello Aditya,

You should not believe any answer keys by any institutes as the final one. But they are also not that bad. I mean apart from 2–3 questions, I was pretty sure that the answers given are correct. You can also check the rank there and get some rough idea. But only rely on official GATE key as that will be the final one.

Talking about the rank prediction so, people say that it is 95% accurate and yes, it is true. Being 95% accurate means variation may occur, but to a very small extent (+50 approx).

Hope this helps.