To deploy the YAML file you need to runs kubectl apply -f file_name.yaml Reference:
https://docs.microsoft.com/en-us/azure/aks/kubernetes-walkthrough

The VMs are in AZ then VPN gateway will have to on AZ which will rely on Azure public IP resource Standard SKU. And must be Static as Dynamic is only for non-AZ.
Reference:
https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/public-ip-addresses#at-a- glance
https://learn.microsoft.com/en-us/azure/vpn-gateway/about-zone-redundant-vnet-gateways

See below explanation
Explanation:
Add a data disk
Step 1. In the Azure portal, from the menu on the left, select Virtual machines.
Step 2. Select the Web01 virtual machine from the list.
Step 3. On the Virtual machine page, , in Essentials, select Disks.

Step 4. On the Disks page, select the Web01-Disk1 from the list of existing disks.
Step 5. In the Disks pane, click + Add data disk.
Step 6. Click the drop-down menu for Name to view a list of existing managed disks accessible to your Azure subscription. Select the managed disk Web01-Disk1 to attach:

References:
https://docs.microsoft.com/en-us/azure/virtual-machines/linux/attach-disk-portal

See below explanation
Explanation:
Task A: Create a Recovery Services vault (if a vault already exists skip this task, go to Task B below) A1. From Azure Portal, On the Hub menu, click All services and in the list of resources, type Recovery Services and click Recovery Services vaults.
If there are recovery services vaults in the subscription, the vaults are listed.
A2. On the Recovery Services vaults menu, click Add.
A3. The Recovery Services vault blade opens, prompting you to provide a Name, Subscription, Resource group, and Location Task B.
B1. On the Recovery Services vault blade (for the vault you just created), in the Getting Started section, click Backup, then on the Getting Started with Backup blade, select Backup goal.
The Backup Goal blade opens. If the Recovery Services vault has been previously configured, then the Backup Goal blades opens when you click Backup on the Recovery Services vault blade.
B2. From the Where is your workload running? drop-down menu, select Azure.
B3. From the What do you want to backup? menu, select Virtual Machine, and click OK.

B4. Finish the Wizard.
Task C. create a backup schedule
C1. Open the Microsoft Azure Backup agent. You can find it by searching your machine for Microsoft Azure Backup.

C2. In the Backup agent's Actions pane, click Schedule Backup to launch the Schedule Backup Wizard.

C3. On the Getting started page of the Schedule Backup Wizard, click Next.
C4. On the Select Items to Backup page, click Add Items.
The Select Items dialog opens.
C5. Select Blob Storage you want to protect, and then click OK.
C6.In the Select Items to Backup page, click Next.
On the Specify Backup Schedule page, specify
Schedule a backup every: day
At the following times: 2.00 AM

C7. On the Select Retention Policy page, set it to 90 days, and click Next.

C8. Finish the Wizard.
References:
https://docs.microsoft.com/en-us/azure/backup/backup-configure-vault

Explanation:
Box 1: User5
In Express settings, the installation wizard asks for the following:
AD DS Enterprise Administrator credentials
Azure AD Global Administrator credentials
The AD DS Enterprise Admin account is used to configure your on-premises Active Directory.
These credentials are only used during the installation and are not used after the installation has completed. The Enterprise Admin, not the Domain Admin should make sure the permissions in Active Directory can be set in all domains.
Box 2: UserA
Azure AD Global Admin credentials credentials are only used during the installation and are not used after the installation has completed. It is used to create the Azure AD Connector account used for synchronizing changes to Azure AD. The account also enables sync as a feature in Azure AD.
References: https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory- aadconnect-accounts-permissions