Istio sidecar injection with different versions of Istio

Hi All, I have an requirement, my current cluster configured with Istio 1.3 to upgrade to 1.8 , we tried this approach instead direct upgrade. I have created new / custom Istio namespace and deployed the Istio 1.8 new namespace both Istio are working fine, but here the confusion how to inject this new istio side car to namespace. 1. can able to use both Istio sidecar injection same time 2 if not how to new istio sidecar injection to specific namespace. please help me on this