This command correctly lists pods that have the label app=prod. When creating the deployment, we used the label app=prod so listing pods that have this label retrieve the pods belonging to nginx deployments. You can list pods by using Kubernetes CLI kubectl get pods.
Ref: https://kubernetes.io/docs/tasks/access-application-cluster/list-all-running-container-images/ Ref: https://kubernetes.io/docs/tasks/access-application-cluster/list-all-running-container-images/#list-containers-filtering-by-pod-label

Reference:
Create a Kubernetes Service of type ClusterIP for your application. Configure the public DNS name of your application using the IP of this Service. is not right.
Kubernetes Service of type ClusterIP exposes the Service on a cluster-internal IP. Choosing this value makes the Service only reachable from within the cluster so you can not route external traffic to this IP.
Ref: https://kubernetes.io/docs/concepts/services-networking/service/

IAP controls access to your App Engine apps and Compute Engine VMs running on Google Cloud. It leverages user identity and the context of a request to determine if a user should be allowed access. IAP is a building block toward BeyondCorp, an enterprise security model that enables employees to work from untrusted networks without using a VPN.
By default, IAP uses Google identities and IAM. By leveraging Identity Platform instead, you can authenticate users with a wide range of external identity providers, such as:
Email/password
OAuth (Google, Facebook, Twitter, GitHub, Microsoft, etc.)
SAML
OIDC
Phone number
Custom
Anonymous
This is useful if your application is already using an external authentication system, and migrating your users to Google accounts is impractical.
https://cloud.google.com/iap/docs/using-tcp-forwarding#grant-permission

This answer is the most effective way to validate whether the service account used by the CI/CD server has the appropriate roles in the specific project. By checking the IAM roles assigned to the service account, you can see which permissions the service account has and which resources it can access. You can also check if the service account inherits any roles from the folder or organization levels, which may affect its access to the project. You can use the Google Cloud console, the gcloud command-line tool, or the IAM API to view the IAM roles of a service account.