IIT Kharagpur - Indian Institute of Technology

Commonly, it is known as Letter of Recognition (LOR). If I am not mistaken. Generally, it is required when you go for higher education. You can check below link for format and more about LOR-
https://studyabroad.shiksha.com/lor-recommendation-letter-applycontent2702.

Taking admission in M.Tech after clearing GATE is easy, and the GATE Score requirement generally depend on your category. If you are talking about general category, the GATE score should be above 55.

You can go for some engineers post in Navy, or if you are interested in some research oriented stuff, you can apply for scientist post. There are many ocean research institutes.

No, you are definitely not eligible. You have to have Physics for 4 semester and Mathematics for 2nd semester in B.Sc. There is no restrictions on +2 subjects.

You should give first JEE Mains & then JEE Advanced to qualify with good marks. Mainly, criteria of eligibility for JEE Main is that open category students at least need 75% score in board exams. Also, OBC category students must have obtained 65-69% marks in board exam. So check with your eligibility firstly. Best wishes for me.

According to me Agricultural engineering from IIT kharagpur is better option than computer Science engineering at CTAE Udaipur because IIT kharagpur has well knowledge staff with well-equipped labs and they also provide good amount of placements to you students. Good luck.

Yes, it's the best choice to do M.Tech in agriculture from IIT Kharagpur as it's among the top colleges in India for pursuing engineering.