We as humans don't differ on what morality is. We differ on the application of it.
If ethics is subjective and based strictly on the social norms of a particular group, then logically speaking there should be nothing to stop people from separating and creating their own equally valuable and subjective social norms and ethics. When this thought experiment is taken to the extreme, different equally valuable and subjective ethical codes may exist but still be in contradiction with one another, hence, all the ethical codes negate one another. Thus ethical subjectivism is ethical nihilism.
Yes. It's how people learn their own mistakes from their surroundings. The environment they born into. An objective becomes as a subjective. It's called learning.
I have yet to find a single objective source of morality. Morality is subjective by nature.
morality is inherintly perception
Of course not because the way morality is usually developed is through standards set by society and our cultures passed onto us by our parents or guardians and within each culture and/or society there is a difference in the standards set.