You’ll be given a chance to switch to another branch after your first year. The process is known as branch sliding, and it will be based on your first year CGPA and the vacancy in your preferred branch.
For Mechanical, try to obtain a 9.2+ CGPA in your first year. For CSE, at least 9.6 is required because there's always a huge competition for this branch. For Electrical, 8.5 is enough. For Chemical, ECE and Civil, an 8 CGPA is enough.
Try to maintain a good score in your first year for a branch switch at SVNIT.