B.Sc Agriculture

Of course, yes. You will get admission in IIT-BHU Main Campus as your general rank is too good. You are eligible to take admission.

Yes,you can. There is no problem in that.

It is based on your point of interest. B.Sc. . in agriculture include more part of Botany while B.Sc. . in forensic Science includes more part of Zoology & Microbiology.

Very good chance. Your daughter will get the desired seat in BHU very easily.

Yes, you will get the seat in BHU and probably in Main Campus too.

B.Sc. Agriculture has a wide scope with Hons in different areas:
In the banking sector like Agriculture officer etc., teaching Professor and assistant professor
Lab technician
Jobs in the input sector like fertilizer, pesticede and Seed industry
Jobs in the food processing industry
and several other