M.Sc Zoology

R. D. Barnes for classification - It may seem or looks like a hard or tough book to see and understand but once you start understanding it's the best book for classification. I'll suggest you to not to go for Kotpal. It's not a bad book, until you have plenty of time to study and analyse, Kotpal is like the Kunji (or guide). Tortora for physiology the best one. Odum for ecology. (Same reason as of R. D. Barnes) or you can go for Srivastava.
Leninger for immunology
For developmental biology, take any good Indian writer by asking your professors, try avoiding foreign writers.

If you see both courses are better at their level, but seeing further with the point of interest, the course which attracts you or you have more interested in any one of them, will be better for you than the other.

If you're asking about DU, they've an entrance test for which you can apply.

For doing M.Sc in zoology from CCS, Meerut, a candidate must have done Bachelor's degree in B.Sc zoology and he/she must have secured 2nd division at 10+2 level from a recognized board.

Yes, you can do M.Sc in Zoology in private mode.

No, they are not related to each other .