The eligibility of BCA is as follows Candidate must pass 10+2 with minimum of 50% from recognised board irrespective of the subjects. So if you have more than 50% you can do BCA

Also you can do Msc Computer science /IT after your 3 year undergraduate BCA .

MSc CS is a 2 year full time  post graduate course.You have to give JAM exam for admissions to Msc .See the link for more details;

https://university.careers360.com/exams/jam

So after your Msc you are eligible to do M.Tech but you need to give a entrance exam for admissions to M.Tech program . The exam is known as GATE

See the link below for more details:

https://engineering.careers360.com/exams/gate

Hope you got your answer.

Thank you