Explanation

Box 1: 6
Two out of three update domains would be available, each with at least 3 VMs.
An update domain is a group of VMs and underlying physical hardware that can be rebooted at the same time.
As you create VMs within an availability set, the Azure platform automatically distributes your VMs across these update domains. This approach ensures that at least one instance of your application always remains running as the Azure platform undergoes periodic maintenance.
Box 2: the West Europe region and the RG1 resource group
References:
https://docs.microsoft.com/en-us/azure/virtual-machines/windows/regions-and-availability

Explanation
After you've configured an Azure resource with a managed identity, you can give the managed identity access to another resource, just like any security principal.
Use Azure RBAC to assign a managed identity access to another resource
After you've enabled managed identity on an Azure resource, such as an Azure VM or Azure virtual machine scale set:
* Sign in to the Azure portal using an account associated with the Azure subscription under which you have configured the managed identity.
* Navigate to the desired resource on which you want to modify access control. In this example, we are giving an Azure virtual machine access to a storage account, so we navigate to the storage account.
* Select the Access control (IAM) page of the resource, and select + Add role assignment. Then specify the Role, Assign access to, and specify the corresponding Subscription. Under the search criteria area, you should see the resource. Select the resource, and select Save.
Reference:
https://docs.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/howto-assign-access

We should use a Conditional Access policy.
Note: There are two ways to secure user sign-in events by requiring multi-factor authentication in Azure AD.
The first, and preferred, option is to set up a Conditional Access policy that requires multi-factor authentication under certain conditions. The second option is to enable each user for Azure Multi-Factor Authentication. When users are enabled individually, they perform multi-factor authentication each time they sign in (with some exceptions, such as when they sign in from trusted IP addresses or when the remembered devices feature is turned on).
Enabling Azure Multi-Factor Authentication using Conditional Access policies is the recommended approach.
Changing user states is no longer recommended unless your licenses don't include Conditional Access as it requires users to perform MFA every time they sign in.
Reference:
https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-userstates Legacy AZ-300: Create and Deploy Apps Question Set 1

Explanation:
VM2: West US
In RG2, which is in West US, you need to create a new virtual machine named VM2.
VM2_interface: East US
VM2 will use a network interface named VM2_Interface to connect to VNET1, which is in East US.
References:
https://docs.microsoft.com/en-us/azure/virtual-network/associate-public-ip-address-vm