Colleges in Kolkata

Heritage institute of technology if one of the best private Colleges of West Bengal. Placement is very good there but just for CS/IT branch.Other branches has average placement.

M.Com will lead you for further higher studies as well as jobs where as B.Ed will only provide you a high school job.

Although it cant be predicted with a certainity, but if you are a boy, you can expect to get through if you have above 93.5%. Girls might need little more than 94.5%. This is because morning batch which is boys only has a little lower cut off due to more seats. Girls can get into evening batch which is co-ed.
Its a great college for B. Com Honours, if you are considering it as an option.

Yes, for biotechnology you need to have a background in physics, chemistry and biology.
You seem to have studied these subjects so you are eligible to pursue biotechnology.

IIHM have no good placements. Also, the degree would be distance learning which is not advisable for HM.

IHM is always better. IIHM is not advisable. There are not affiliated to any university for formal degree. Please avoid if possible. It's a distance learning degree which is not allowed by UGC for HM.