Explanation:
Box 1: No
An Azure AD tenant can have multiple subscriptions but an Azure subscription can only be associated with one Azure AD tenant.
Box 2: Yes
Box 3: No
If your subscription expires, you lose access to all the other resources associated with the subscription. However, the Azure AD directory remains in Azure. You can associate and manage the directory using a different Azure subscription.
References:
https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/active-directory-how-subscriptions-associated-directory

Explanation
In Azure you only pay for outbound traffic which is charged in GB as you are entitled to 5GB in a month but afterwards you pay for data being transferred out. However, with inbound data traffic into your environment, this is free.

Reference:
https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-overview
https://www.codeisahighway.com/effective-ways-to-delete-resources-in-a-resource-group-on-azure/