GATE

No, your B.Tech percentage is good but for M.Tech, you have to score well in the GATE exam in order to get a good college and better future.

With GATE examination, you have two following major benifits: (a) You will able to get admission in top CS institutes of India such as IITs, IISc, NITs, IIITs, etc. which will build a solid foundation for your IT career in Large IT firms and MNCs.
(b) Based ofnGATE score, you can get job in many Public Sector Units.

It will depend on your category, the number of candidates applying and the difficulty of questions then the cut-off will decide by the board. This is the reason of change in cut-off every year.

All institute who take admission through GATE scores are not providing stipend however all NITs , IITs, IIITs and most government engineering colleges provide stipend. For more detail you may go through institute website and contact them by finding contact information.

Kindly clear the college you are seeking for.

Its vary and depends upon the branches also. Any GATE score more than 400 have good chance to get admission.