Reference:
https://docs.microsoft.com/en-us/graph/permissions-reference

Explanation

Box 1: Yes
Extensions are client-side components that run inside the context of a SharePoint page.
Box 2: Yes
ClientSideExtension.ListViewCommandSet.CommandBar: The top command set menu in a list or library.
Box 3: Yes
ClientSideExtension.ListViewCommandSet.ContextMenu: The context menu of the item(s).
Reference:
https://docs.microsoft.com/en-us/sharepoint/dev/spfx/extensions/get-started/building-simple-cmdset-with-dialog-

Topic 1, ADatum Corporation
Existing Environment
Application Architecture
E-invoicing consists of a single-page application (SPA) and a backend web service that provides invoice management and processing functionality.
E-invoicing stores all the details of each invoicing operation in a backend cloud database. E-invoicing generates invoices in PDF format and provides users with the ability to download the PDF after it is generated. Each invoice has a unique identifier named invoiceid.
The users have a common workflow where they sign in to E-invoicing, and then open E-invoicing in multiple tabs of a web browser so they can use different parts of the application simultaneously.
Security Architecture
ADatum uses the principle of least privilege whenever possible. ADatum always uses the latest libraries and integration endpoints.
Requirements
Business Goals
ADatum wants to integrate E-invoicing, Azure Active Directory (Azure AD), and Microsoft Graph so that their customers can leverage Microsoft Office 365 services directly from within E-invoicing.
Planned Changes
ADatum plans to add the following capabilities to E-invoicing:
Email the generated invoices to customers on behalf of the current signed-in user. Any emails generated by the system will contain the invoiced.
Perform as many operations as possible in the browser without having to leave the E-invoicing application.
Use Azure AD to manage identities, authentication, and authorization.
Display all emails that contain a specific invoiced.
Technical Requirements
ADatum identifies the following technical requirements for the planned E-invoicing capabilities:
Ensure that all operations performed by E-invoicing against Office 365 are initiated by a user. Require that the user authorize E-invoicing to access the Office 365 data the first time the application attempts to access Office 365 data on the user's behalf.
Send scheduled reminders to customers before a payment due date. Create an administration user interface to enable the scheduled reminders.
Implement Microsoft Graph change notifications to detect emails from vendors that arrive in a designated mailbox.
Implement single sign-on (SSO) and minimize login prompts across browser tabs.
Secure access to the backend web service by using Azure AD.
Ensure that all solutions use secure coding practices.
Backend Security Planned Changes
ADatum wants to use custom application roles to map user functionality to permissions granted to users.
E-invoicing will have internal logic that will dynamically identify whether the user should be allowed to call the backend API.
SSO JavaScript Script
You plan to implement SSO with Microsoft Authentication Library (MSAL) by using the following code:

Access Token JavaScript Script
You have the following JavaScript code to obtain an access token.

Change Notification JSON
You have the following JSON message that will be sent by the Microsoft Graph service to detect the vendor emails.

The AadHttpClient client object is useful for consuming any REST API. You can use it to consume Microsoft Graph or any other third-party (or first-party) REST API.
To consume any REST API using the AadHttpClient client object, create a new instance of the AadHttpClient type by calling the context.aadHttpClientFactory.getClient() method and providing the URI of the target service.
Reference:
https://docs.microsoft.com/en-us/sharepoint/dev/spfx/use-aad-tutorial