Biology

That totally depends on you because if you choose biology, you may become a doctor/nurse and if you choose fashion designing, then you become a fashion designer.
In my opinion, you should opt biology because fashion stream is not reliable. Very few people can make their career in this field and also, fashion changes so rapidly that not everyone can manage it. But if you opt for biology and become a doctor and for once, let's assume you can't get a job, you can still open your clinic.
So, that is a much satisfactory course than fashion designing.
Hope this helps.

Courses and careers after 12th Science, biology group:
MBBS (Bachelor of medicine, Bachelor of surgery)
veterinary sciences
bams (Bachelor of ayurveda, medicine and surgery)
bds (Bachelor of dental surgery)
pharmacy
Pharma.D
B.Sc
bums (Bachelor of unani medicine and surgery)
bhms (Bachelor of homeopathic medicine and surgery)
Bachelor of physiotherapy
baslp (Bachelor of audiology speech language pathology)
Bachelor of occupational therapy
paramedical courses.

How can one possible say what you have to study without knowing your future plans? B.Sc is a very generic term.

https://www.shiksha.com/university/university-of-delhi-24642
Please go to the link I am sharing here to know about fees structure of Delhi University. Here you will get all information about the admission.
Good luck.

The number of candidates is not disclosed, so nobody can share this information.

Yes, biology will be the base course to apply for an integrated course in biology.

Yes, you can become eligible to apply for MD degree after acquiring a PR status.

Yes, for B.Sc in agriculture, having biology is necessary.