I'm running my service at K8S on-prem, is there any way to deploy my service (such as an eComm website) accross K8S on-prem and public cloud's K8S (for example Google Compute Engine run K8S or GKE) as hybrid K8S?
Can K8s (or Istio) support this kind of requirement for two different location?
If I understand you correctly the answer is yes.
According to the GKE documentation.
GKE On-Prem is hybrid cloud software that brings Google Kubernetes Engine (GKE) to on-premises data centers. With GKE On-Prem, you can create, manage, and upgrade Kubernetes clusters in your on-prem environment and connect those clusters to Google Cloud Console.
You can find the Overview of installation here. And rest of the documentation here.
As for Istio:
Istio is an open source framework for connecting, monitoring, and securing microservices, including services running on GKE On-Prem.
Please let me know if that helps.