Hello,
#1 (This is only an assumption). I'm not entirely sure that Microsoft would allow the complete deletion for auditing reasons. It is quite possible that people with ill reasons could create Azure services, abuse them, then completely delete wipe their trail.
#2 As stated in the documentation, you can close your Microsoft Account:
#3 When you delete your subscriptions, it effectively deletes all of the information for you to access and shuts down all the services related to the subscription.
If this is helpful please accept answer.