How to set up environments properly in Istio

Hi, We are new to ISTIO and just starting to plan our deploy across all environments. What is the best way of setting up Test, Stage, Performance and Production in ISTIO? Do you install ISTIO for each environment and is this even possible? Or do we just install one ISTIO and that should have all of the environments in it(done this already)? But how do you do upgrades or maintenance on ISTIO without impacting the other environments? Thanks.