As a former B.Tech student at MNNIT Allahabad, here is my advice on this matter-
To switch to some other branch from Production Engineering, you need to study hard during your first year. You don’t need to study as much as you did while preparing for your JEE, but you’ll have to work harder than your peers. It also depends on the number of vacant seats in the branch you wish to switch to. Many times, CS witnesses zero vacancies for branch sliding.
But do not spend all your time worrying about branch sliding. Enjoy your stay at the fresher hostels, as they are the best ones. Participate in tech events like ‘Avishkar’ and make good use of the 24*7 wifi connectivity.
Study for at least 4-5 hours a day, and score 8.5+ CGPA during first year to at least have fair chances at branch sliding.