BCA

Following are best MCA colleges/ universities based on ranking and placement records:
(a) Department of Computer Science, University of Delhi
(b) Jawaharlal Nehru University - New Delhi
(c) Birla Institute of Technology (BIT), Ranchi
(d) Hyderabad Central University
(e) National Institute of Technology (NIT), Trichy
(f) National Institute of Technology (NIT) - Surathkal
(g) PSG College of Technology - Coimbatore
(h) NIT- National Institute of Technology, Rourkela
(I) MN National Institute of Technology (NIT) - Allahabad
(j) Vellore Institute Of Technology - Vellore (Tamil Nadu)
(k) Manav Rachna International University

No, it's not possible. To pursue M.Tech, you need to have a B.Tech degree.

Web development is quite a crowded space. To break into web development as individual consultant or job is difficult because of lots of competition from B.Tech, MCA, BCA, B.Sc CS/IT, Diploma etc candidates. Anybody who wants to become Web developer must have very good understanding of html, css and javascript. In addition it is necessary to learn at least the basics of jquery.Basic understanding of MYSQL will be very helpful. Base on these basics you can learn PHP, Python, Ruby etc.

Yes, you are eligible for pursuing BCA being the biology student, but you should have at least 45% in aggregate.
Being of any discipline, you can apply for BCA.

As BCA and BBA are different field graduation degree with minimal overlap in syllabus in first year, it may be difficult for you to seek lateral entry admission in BBA after completion of first year in BCA.