Sir, i have got 63.83 percent in 10 class and i want to study in b tech

Yes, You can study B Tech there are many colleges which does not demand 75% or in top 20 percentile for admission to undergrad engineering courses. Institutes such as Manipal, VIT, SRM, MIT Pune does not have a very strict rule for class 12th performance, You can go for these Institutes and they have the same reputation as NITs. The only drawback with this marks is that You can not go to IITs. Anyways good engineers are made in every college so it all depends upon your passion.

IIT JEE is the National Level Exam to pursue the engineering programme. There are many other Engineering Entrance Exam like VITEEE, BITSAT, AEEE, SRMJEE & other state level Entrance exams But you should be passed or appearing class 12th, If you wish to get admission in IITs, NITs, IIITs, GFTIs, You should have minimum 75% in class 12th as a General category or you should be in top 20 percentile in your class XII exam conducted by the respective board.

Good Luck!