Can I pursue M.Sc in zoology after completing B.Tech in biotechnology as I want to become a zoology lecturer?

Yes, you can do that but there are only certain universities which offer this condition. You need to explore more. You can check it out in DU and JNU.

Yes, I think you can but a few universities have rules to take students in this case. You can check some of the universities like JNU, BHU, DU, Central University of Rajasthan and Central University of Gujarat.