Single/Extended License is valid for single end-product (production version) as well as that end-product staging, local & pre-prod.
It’s not required to purchase a separate license for en-product sub-versions like staging, local & pre-prod.
Suppose you have purchased a Single/Extended License for your end-product which will be hosted on my-domain.com, then you can also use it for
localhost/
staging.my-domain.com/
test.my-domain.com/
But you can't use a Single/Extended License for multiple end-product/domains. For ex:
my-domain.com
other-domain.com