It doesn't matter if you know anything or not regarding Computer Science. The thing is that the curriculum is so designed that you will get the knowledge from your curriculum. So don't take stress about that. The things you should know is Mathematics. Coding refers to mathematical models and ideas of Discrete Mathematics. So it would be helpful for you to have a good mathematical skills. Although you will get enough scope to learn mathematics but having a good skills of 10+2 level Mathematics can be beneficial for you.

For more information regarding BTech in Computer Science & Engineering consider the link below:

https://www.careers360.com/courses/b-tech-in-computer-science-and-engineering

I hope this helps. Wish you a great day!