JAM

Yes, maths is necessary in 12th standard for IIT. As you are interested in Biotechnology, please search for institutions, which don't require maths as a subject.

Hello,
Yes, you can apply.
You just need a graduation degree with minimum 55% marks for General & OBC and 50% marks for SC, ST categories from a recognized university.
But if you wan to appear in the IIT JAM Exam, then you must also satisfy all the other eligibility conditions. Check all the conditions regarding IIT JAM Exam here: https://goo.gl/fNdqWo IIT JAM 2018 Exam has been conducted on 11th February 2018.
So, if you wan to appear in the IIT JAM Exam, then you can appear in the 2019 Exam.
IIT JAM 2019 Exam will be conducted in the month of February 2019. So, you have enough time for the preparation.
Best of Luck!

Yes, you can get admission in IIT Delhi, but it may somewhere struggling for CS branch.

It will be better if you go for a graduation related to Mathematics. Because it will eventually help you in your preparation for IIT JAM Mathematics.

There is no need for science stream, but you have coding skills hence you are eligible.

Both are better but IIT, Bombay gives better placement than IIT, Kanpur. The infrastructure of IIT, Bombay is also better and it is listed in top 10 universities of India.