Is the blastocyst a human being? Then, yes. They have human rights. It is unethical to experiment upon human subjects without their consent and where the experiment is likely to cause their injury or death.
If so, is there any stage in the reproductive cycle where discrete cellular development is without rights?
"Reproductive cycle", and "discrete cellular development" are too ambiguous for me to be able to know precisely what you are asking. Perhaps you could give me an example.
Cordially,
Spermatagonia. Spermatozoa. Ova.