Hii

After BCA you can not apply for M.tech through GATE, but for private colleges you need to contact them if they allow you for M.tech.  You can go for MCA, it is a good option & MCA is an advanced and more detailed version of BCA course. The program has the topics such as Software and Applications Development, Hardware, Networking, Mobile Computing, Computer Science, Programming languages, Algorithm, Internet Technologies etc.

Here are the colleges you can prefer:

Pune University Computer Science Department

School of Computer and Systems Sciences (Jawaharlal Nehru University)

All the best.

No, first you have to do btech.