@PK AFAIK there isn't any built-in support for cloning a resource group. You could always export a resource group as an ARM Template but it won't really help to clone immediately.
You could leverage ARM APIs to perform cloning, but I believe this would require some work to get it right for all resources involved.
The recommended approach would be to author ARM templates (you could build upon the exported ones above) and deploy your resources for each environment as required. Azure APIM has an official doc that covers how you can setup CI/CD for APIM that you can refer to as well.