Diploma

Yes, there are many university which providing Master and PhD level program in distance or part-time mode. You may visit the website of Indra Gandhi Open University for eligibility criteria in your field of studies.

If you are a topper students and want to do diploma, you should appear for entrance test conducted by different institutes. Good colleges take admission on the basis of entrance exams and not on the basis of marks.

You may got a job in government and private hospital as a technician. People are getting good salary approximately 15 to 40 thousands after completing diploma in radiology therapy even in private hospital.

You can get good private college, but now a days getting into a college is not important thing. The important is which branch you choose.
Computer Science and Automation and Robotics are two branches having great scope in future.
I would suggest Gulzar Group of Institution for these two branches as, G

There are many institutes which provides part-time BE course for working people. You should find some colleges near you and find out the B.E program. As you have experience, so you will get edge in admission.

You are eligible to take admission in any field of engineering after completing your Diploma engineering in any stream. However, you should try mechanical or chemical engineering to utilized your Diploma level knowledge.

No, it is a certificate course. No Diploma is equivalent to a degree course. It is equivalent to 12th only if it is a 3 years course.

If you are not hurry in getting a job than you should go for 11th science then after your intermediate you may go for B.Tech in computer science. However, you should appear for different entrance tests of Diploma so that you have some options, in case if you are not getting admission in the college

Diploma is equivalent to intermediate but it is a 3 years professional course. Certificate course is a short term course in a particular topic or field. Advance or PG diploma is a Diploma course which you pursue after your degree. You should complete your diploma or intermediate then you may go Cana

Post Graduate Diploma in International Business (PGDIB) - is two year course.
Any graduate (with 50% aggregate marks) from any recognised Indian/Foreign University shall be eligible for admission to the course.