IIT

You need to qualify JEE Mains exam to get admission in NITs and JEE Advanced exam to get admission in IITs.
Kindly visit the link mentioned below to know about the colleges offering B.Tech in biotechnology:
https://www.shiksha.com/top-bio-technology-colleges-in-india-rankingpage-54-2-0-0-0

My recommendation on your choices is as follows in order of precedence: IIT, NIT, VIT. These are based on brand image, career opportunities, growth and other factors.

Hi,
It entirely depends on the cut off of that particular year. But getting 230+ would ensure your admission in CS in good NITs. In case of IITs you need to just qualify JEE Mains but have to do well in JEE Advanced.

Different IITs are good for different branches. You may use the following link by changing filter to get the best IIT with respect to major branches of engineering: https://www.shiksha.com/top-engineering-colleges-in-india-rankingpage-44-2-0-0-0

You have to appear for JEE Advanced to get admission into IIT. In JEE Mains you have to secure a very good score, so that you get eligible to appear in Advanced.

PEC University, Chandigarh and IIST are two good options for aerospace engineering among government colleges. You can also consider Amity university and Manipal University among private universities.

You can refer to the following textbooks:
1. Cengage for mathematics.
2. Dr. OP Tandon for chemistry.