Box 1: No -
Online migration will work fine. It does not require an Azure Storage account.
Box 2: No -
Data for the web site can migrated to Azure app service.
Box 3: Yes -
Scenario: Database metrics for the production instance of WebApp1 must be available for analysis so that database administrators can optimize the performance settings.
Reference:
https://azure.microsoft.com/en-au/services/sql-server-stretch-database/