CBSE 12th

Hello Aditya,
No, 10th or 12th class marks are not considered during admission into MIT. All you need to do is to take some tests.
1) The SAT or ACT, as well as two SAT subject tests, one in Math ( level 1or 2 ) one in Science (physics or chemistry or biology).
2) The TOEFL (MIT does not accept IELTS as well as two SAT subject tests, one in maths (level 1or 2) one in science (physics, chemistry and biology). This is especially recommended who do not speak English at home or in school, or who have been speaking English for fewer than five years.
Requirements for application:
GPA requirements
Testing requirements including SAT and ACT.
Application requirements.
To get into a college, firstly look at the acceptance rate which is 8% i.e for every 100 applicants only 8 are admitted.
Meeting GPA and SAT/ACT requirements are very important for getting into a college.
The average GPA is 4.13. This means you need nearly straight As in all your classes to compete with others.
The average SAT score is 1520 on 1600 SAT scale. The score makes MIT extremely competitive for the SAT scores.
-Avg ACT score is 34. Taking ACT tests, you are at the huge advantage as it offers 10 tests, in which you will be required to send you the highest of those ten tests.
Hope this helps.

Yes, you can appear for IIT-JEE examination after the completion Diploma of engineering or in the last year of Diploma. Through this examination you will be able to take admission in IIT in first year of engineering like a 12th pass students. You can choose any branch of engineering irrespective of your branch of engineering in Diploma. But it will be better for you if you choose the branch in IIT related to your branch in Diploma. There is no lateral entry seats in IIT. So, you can not take admission in IIT directly in the second year of engineering in any way. The only way to take admission in graduation course of engineering is to clear the IIT-JEE entrance examination. IIT-JEE examination is little bit tough examination and competition is very high. You must be well prepared before appearing in the examination. Beside this examination, you may appear in the Lateral Entry Entrance Test (LEET) to take admission in the second year of engineering in other engineering colleges. This is a state level examination. If you can clear this examination then through counselling, you will be able to choose a college from your state to take admission in the second year of engineering. It will save your one year.