Activating Orchestrator Licenses to each instance

Hello all,
Hope not repeating this subject…
Recently we have installed and configurated orchestrator and studio according 3 environemts, dev, non-prod and prod, each machine within azure vm. This result on 3 orchestrator instances and according the license certificate those instances has the same license key.
I was able to activate the license in one instance only. Than I read, How to create Orchestrator instances of Development, Acceptance and Production. Do we need to buy license for each instance? With one orchestrator license can we create instances, and realized probabely I have to ask for the others licences key.

How it works exactely ?