Does M.Tech course ever had a duration of 4 years? When did B.Tech and M.Tech courses began in India?

M tech is only for 2 years of study.

No, B.Tech course are of 4 years and M.Tech are of 2 years if you pursue individually but if you pursue B.Tech +M.Tech it takes total 5 years by which you can save 1 year.

First of all you have to pursue B.Tech which is a 4 years course. After that you have to qualify in GATE examination. Then you can opt for M.Tech which will require another 2 years I. e. , total 6 years for getting both B.Tech and M.Tech.