Civil Engineering

After having Diploma in CSE then it will be better B.Tech in CSE. This will give him a career in continuation with specific skills. Changing stream is not a good idea after completing Diploma with 60% marks.

You need to appear for BIT – SAT entrance exam to get admission in BIT, Mesra.

It basically depends on your interest. You can opt for GATE exam to pursue M.tech in any particular field or either go for CAT and look forward to MBA.

You can do certicate courses like- MS-Cit, tally, mobile repairing, etc. If you're a engineering graduate, you can do autocad. If you're a MBA finance graduate, you can do SAP FICO courses, typing courses, etc.

It varies from Institution to institution. Inquire with the institutions of your choice

As currently, you are working. It means, you cannot join full time course. Better to think from AMIE (Institution of Engineers) as with any other universities in distance, your diploma course will not be valid with AICTE.

RWTH Aachen University is the largest university of technology in Germany and one of the most renowned in Europe. It has approximately 42,000 enrolled students, most of them in the field of engineering. Scientists come to the university to benefit from its high quality courses and excellent facilities, both of which are recognized at an international level.
In Indian cooperate world is not renowned but yes, it can help you. Career opportunity depends on you.

Kindly refer the following institutes :
Pratham Institute of Education, Lajpat Nagar, Delhi
R&R Education Foundation, Rani Bagh, Delhi
International Institute of Management and Technical Studies, Bhopal
Wisdom School of Management, Gwalior
Academy of Higher Education, Borivali East, Mumbai

Civil engineering have its own importance Akshay. I would suggest that you should move to newly formed Indian states because these states like Chhattisgarh, Jharkhand, Uttarakhand and Telangana have wide scope for civil engineers. Even, you can go for higher studies or even prepare for civil services.
You can have a collaboration with architects to help you earn also.
Best regards.

Diploma in engineering is not a graduation. So, its not a criteria for Master's degree. For a masters degree, you must have a bachelor's degree. Rather, you can opt for BE, you will get admission in 3 semester. After completion of BE or B.Tech, you can surely go for MBA.