Explanation
In IaaS, the service is bare metal, and the customer has to install the OS and the software; the customer then is responsible for maintaining that OS. In the other models, the provider installs and maintains the OS.

Explanation
Authentication goes a step further than identification by providing a means for proving an entity's identification. Authentication is most commonly done through mechanisms such as passwords. Identification involves ascertaining who the entity is, but without a means of proving it, such as a name or user ID.
Authorization occurs after authentication and sets access permissions and other privileges within a system or application for the user. Proofing is not a term that is relevant to the question.

The contract should include requirements for notification by the cloud provider to the cloud customer upon the receipt of such an order. This serves a few important purposes. First, it keeps communication and trust open between the cloud provider and cloud customers. Second, and more importantly, it allows the cloud customer to potentially challenge the order if they feel they have the grounds or desire to do so.

Explanation
The functions of the management plane are typically exposed as a series of remote calls and function executions and as a set of APIs. These APIs are typically leveraged through either a client or a web portal, with the latter being the most common.