Mechanical Engineering

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You have to apply as foreign candidate in exam forms. Cost may be high for foreign nationals as compared to indian students. Mechanical engineering fee varies from college to college. If you are looking for government college, it may cost 20 k - 6 Lacs rupees. For private it may cost 5 - 10 Lacs. I will suggest you to give exams like JEE Mains for getting good government college.

Your marks in Diploma & B.Tech is good and above minimum requirement i.e. 60 %. Make sure you are eligible in other criteria also like age, martial status, etc.

BE or B-Tech in mechanical engineering with at least 50% aggregate. Some colleges may require 60%.

Graduation (min 3 years) in any discipline with min 60% marks and have passed Maths and Physics as subject at 10+2 level B.E/ B.Tech from a recognised University with min 60% marks. Age Limit : 20 to 24 years
These are the eligibility criteria.

Yes, there are some government / private colleges in India which provides part/distance time education. Like Anna University etc.

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It depends on the college. But, it generally ranges between INR 4-7 Lacs.

Mechanical engineering & Mechatronics are quite different. As mechanical deals with machine, system, operation, process, etc. Whereas mechatronics deal with mechanics, electronics & artificial intelligence.

There is no entrance exam. Admission is based on the marks you have scored in Diploma.