M.Sc Zoology

Yes prasannna you can appear with environmental Science as a subject because there is no specific subject for zoology. Candidates securing at least 55% marks in their Master's Degree or equivalent from a recognised university in Humanities (including languages), Social Science, Computer Science and Applications, Electronic Science, etc. Are eligible to appear for the UGC NET exam conducted by NTA.

Dear Samiksha, SEE M.Sc. Zoology is a non-professional course so placement chances are not so bright no matter which institute you are opting unless its some foreign University/Institute. IIPS is a private organisation
Please check out the below link to get all the details about IIPS Lucknow
https://www.shiksha.com/college/indian-institute-of-professional-studies-Lucknow-22000/placement.

Have no idea but good placements are offered by Chandigarh university.

No, there is no any such type of criteria. You have to appear in entrance.
You may refer some other private universities for open councelling,in open councelling you take direct admission on the basis of your eligibility.

No, class 12th marks are not needed. If you are not a graduate of Delhi University, the admission is purely entrance-based.