The following chart shows the list of roles and the supported actions on management groups.

Note:
Each directory is given a single top-level management group called the "Root" management group. This root management group is built into the hierarchy to have all management groups and subscriptions fold up to it. This root management group allows for global policies and Azure role assignments to be applied at the directory level. The Azure AD Global Administrator needs to elevate themselves to the User Access Administrator role of this root group initially. After elevating access, the administrator can assign any Azure role to other directory users or groups to manage the hierarchy. As administrator, you can assign your own account as owner of the root management group.
Reference:
https://docs.microsoft.com/en-us/azure/governance/management-groups/overview

Reference:
https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-howto-site-to-site-resource-manager-portal

As App1 is public-facing we need an incoming security rule, related to the access of the web servers.
Scenario: You have a public-facing application named App1. App1 is comprised of the following three tiers: a SQL database, a web front end, and a processing middle tier.
Each tier is comprised of five virtual machines. Users access the web front end by using HTTPS only.

Change the Service administrator for an Azure subscription
Sign in to Account Center as the Account administrator.
Select a subscription.
On the right side, select Edit subscription details.
Scenario: Designate a new user named Admin1 as the service administrator of the Azure subscription.

Azure DNS supports importing and exporting zone files by using the Azure command-line interface (CLI). Zone file import is not currently supported via Azure PowerShell or the Azure portal.