Mechanical Engineering

See, in the mechanical branch, you can't get placements other than from your college as it is very hard to find that but as a electronics engineer you can easily grab a good job and also the promotion in this filed is also quite good.

No, both the steams are totally different but in the 1st year of any stream, you will study the basics of all the branches.

You can pursue automobile engineering. The eligibility of the same is as follows:
The students, who wish to pursue automobile engineering, should have qualified class 12th with minimum 50% marks in Physics, Chemistry and Mathematics from a recognised board in India. Candidates, who wish to join IITs, should have cleared JEE Main and Advanced. Whereas, admission to NITs depends on candidate's JEE Mains score.

Yes, it is possible as you are equivalent to an SSC qualified, follow the needful procedures and seek admission.

For Diploma, you need to complete class 10th and qualify an entrance exam. After completing Diploma, you can do BBA.

For your query, let me tell you that you only need to clear a state level entrance exam for Diploma in which you will get a college based on your rank, but I would suggest you that Diploma is to be done after class 10th, now if you go for Diploma, you'll give your 3 years there and then do B.Tech of four years, so instead of this after 12th, you can directly for B.Tech of 4 years, you would save 2 years.

You should give an entrance exam and bas3ed on the rank, you can get admission for Diploma course.

It depends on the university, generally, they say you should not have any backlogs in exams and a valid reason then a committee looks into the matter and decides what to do.

As per my knowledge and my opinion, for M.Sc you must have a graduation degree. There is B.Sc Degree, because for M.Sc, you must have a B.Sc Degree with 45% marks in your graduation.