See solution below.
Explanation
Add a slot
1. In the Azure portal, search for and select App Services and select your app az400-11566895-main.

2. In the left pane, select Deployment slots > Add Slot.

3. In the Add a slot dialog box, give the slot a name, and select whether to clone an app configuration from another deployment slot. Select Add to continue.

4. After the slot is added, select Close to close the dialog box. The new slot is now shown on the Deployment slots page.

Reference:
https://docs.microsoft.com/en-us/azure/app-service/deploy-staging-slots

Explanation
Feeds have four levels of access: Owners, Contributors, Collaborators, and Readers. Owners can add any type of identity-individuals, teams, and groups-to any access level.

Reference:
https://docs.microsoft.com/en-us/azure/devops/artifacts/feeds/feed-permissions

Explanation
BE: An app deployed to Azure can take advantage of Managed identities for Azure resources, which allows the app to authenticate with Azure Key Vault using Azure AD authentication without credentials (Application ID and Password/Client Secret) stored in the app.
* Select Add Access Policy.
* Open Secret permissions and provide the app with Get and List permissions.
* Select Select principal and select the registered app by name. Select the Select button.
* Select OK.
* Select Save.
* Deploy the app.
References:
https://docs.microsoft.com/en-us/aspnet/core/security/key-vault-configuration
https://docs.microsoft.com/en-us/azure/key-vault/general/tutorial-net-virtual-machine

Explanation

You can set up a CI/CD pipeline to deploy your apps on a Kubernetes cluster with Azure DevOps by leveraging a Linux agent, Docker, and Helm.
Step 1: Create a service principle in Azure Active Directory (Azure AD) We need to assign 3 specific service principals with specific Azure Roles that need to interact with our ACR and our AKS.
Create a specific Service Principal for our Azure DevOps pipelines to be able to push and pull images and charts of our ACR.
Create a specific Service Principal for our Azure DevOps pipelines to be able to deploy our application in our AKS.
Step 2: Add a Helm package and deploy a task to the deployment pipeline This is the DevOps workflow with containers:

Step 3: Add a Docker Compose task to the deployment pipeline.
Dockerfile file is a script leveraged by Docker, composed of various commands (instructions) and arguments listed successively to automatically perform actions on a base image in order to create a new Docker image by packaging the app.
Reference:
https://cloudblogs.microsoft.com/opensource/2018/11/27/tutorial-azure-devops-setup-cicd-pipeline-kubernetes-d