MCA

From your options it is assumed that you want to be a software engineer. B.Tech CSE or B.Tech IT is the most accepted qualification by Indian IT industry for Developer jobs. It will take 4 years to do B.Tech. BCS-MCA duration is 5 to 6 years. Therefore, it is recommended that you opt for B.Tech CSE or IT from good engineering colleges.

Check out the eligibility for BHU MCA PET 2017 and apply accordingly:
Bachelor degree under at least 10+2+3 pattern in any discipline with a minimum of 50% marks in the aggregate, (including all subjects studied at Bachelor's level except those subjects where only pass marks are required and which do not contribute to the total in the final (degree) mark-sheet) with Mathematics as one of the subjects at either Intermediate or +2 (10+2) or equivalent examination, or, Bachelor level (as a main or a subsidiary subject).

Hello Krishna,
If you had mathematics as a subject in class 12th, then you can apply for MCA.
I hope it helps If you have any further questions, kindly revert.

The normal duration of BCA and MCA degree courses is 3-years each. Some universities provide lateral entry admission in MCA to BCA graduates, in that case the duration of MCA is 2-years.

Yes, there is vacancy for a scientist post in ISRO for MCA qualified students.

M.Tech is a good option among the three. You will get opportunities in PSUs as well as in Private sector. IITs are good to pursue M.Tech. A good score in GATE will make you eligible for PSUs interviews.

Hello Utsav,
Diploma is at best considered equivalent to 12th class. Hence, you will have to do graduation first and then only, you can go for post-graduation.