i hve got 183 marks in jee main and 93% in isc board i am general which nit can i get at best if i dont get core branch can i upgrade it in the college how?? please help

You have good chances of getting in topranked NITs but cannot assure you in getting in so called top branches (cs,ec ee,mech...). As you asked about branch change i.e., upgradation after getting into college is not an easy task. You should work hard, really hard for that as you should get CGPA above 8 (this is minimum range).Its all depends on your dedication and working factors after the entrance into the college. This is jst an info to you and not showing the direction.All the best.