CBSE 12th

For colleges, you should clear JEE exam and then go for the counselling in which the colleges will be allotted to you.

Hello Rahul, It's very nice to hear from you that you are interested in doing one year Diploma courses for which qualification is either 12th or graduation. I must congratulate you for thinking on these lines. One must keep on enhancing one's qualification every year. I will advise you that please download brochure cum application form of IGNOU. This university offers a very wide variety of courses. Select the one that you like. Best wishes.

Hello Shobhit,
Yes, you can. Since the minimum percentage in board exams to get admission with JEE scores through JoSAA counseling is 75 percent. Hence you can apply for admission at NITs.
All the best!

Yes, definitely you can do marine engineering as your percentage in class 12 is very good.

For which stream you are interested to take admission?

Yes. Science students can take either of the three stream subjects in their graduation.

Dear, you can wait for the cut-off but if you are belonging to reserved category then you will get a seat in first cutoff.
All the best.

Yes dear, you can study there by qualifying IELTS with good band. All the best.

Yes.
For admissions into BBA courses, students are needed to clear the 10+2 or equivalent examination from any recognized board or school. Some colleges consider the criteria of securing 50% marks in the qualifying exam. The age should be between 17 to 25 years