It is well known that buying an unweaned baby is a huge risk. It is a practice that I do not support, and almost all sellers who practice this are unethical, uneducated, selfish, and shouldn't be producing babies at all. Selling eggs would be simply an extreme version of selling unweaned where 99% of eggs do not survive to hatch, and 99% of hatches do not survive to weaning, and 99% of surviving babies are developmentally damaged. That would mean something like.... 0.000001% of babies sold would live good and normal lives? Is that the right amount of zeros? So no, no one who would engage in that kind of a practice can also be trusted not to cheat you.
Also, buying younger does nothing to increase bonding. Often the exact opposite is true because the baby views the hand raiser as a parent instead of a potential mate or friend.
If you want to do this as some sort of science exerpeiment, go get a chicken egg. Much easier to keep alive, much easier to meet the needs. And then keep that chicken alive, happy, and healthy, just as you would any pet that was so important to you that you had to get it before it hatched.