Test an already existing hypothesis but in a different setting/country? What if I conduct a study and suggest a hypothesis to test but later find out that this hypothesis was already tested before in a different industry/country. Can I still continue? In other words, is there such a thing as plagiarism in stating the same hypotheses?

I find it a burden to go and check the web for every hypothesis I write to see if someone else tested it before. Even though I am sure there are some common hypotheses and studies (like: customer loyalty leads to customer retention, albeit in different industries and/or countries) but I still have doubts.
I think you have a big misconception of what plagiarism is. Passing other people's work as your own is plagiarism; doing something and later discover that it was done before is not. It is not even unethical.

The worst case is that your work is rendered redundant, but this depends on how different your settings and results are.