Hello Ayush Arya,

With 851 as your SC rank. It won't be that difficult for you to rank a government. I would personally suggest to opt for Computer Science and Engineering as a stream if you have no specific inclination towards a specific discipline.

With your rank, your best chances are CSE in Motilal Nehru National Institute of technology, Allahabad, NIT Jaipur, NIT Rourkela etc.

Hope that helps. Do attend your counseling and proceed till the last round of the same. You might never know what might work north for you.