Hello,

After BTech, you can only do MTech. MSc is not allowed in India. if you want to do MSc then you have to apply in aboard.

as your question is not clear and so far it is understandable, you are asking for Mtech at IIT, for get an admission you have to score a good rank in GATE exam. GATE exam is only exam considered for admission for MTech at IIT,NIT, IIIT , government and private colleges.

To  stay in safe site and get top IIT campus, you have to score above 600. for more details about current year cutoff, please go through the link below:-

https://engineering.careers360.com/articles/gate-cutoff

Hope it helps!