Comprehensive Explanation: According to the reference, "Hierarchy sets store the parent-child relationships between nodes of node types defined for a dimension. You can manage multiple hierarchies in a single hierarchy set." The other statements are false. Hierarchy sets are not always a component of a viewpoint's data chain, but only when they are selected as a data object for the viewpoint. Shared nodes exist when the same node is used in multiple hierarchy sets, not when the same node type is used.

1. The request is escalated to a data manager, who grants an exceptional approval and commits the request: This option is correct because when there are not enough approvers available to satisfy the terms of the approval policy, the request is escalated to a data manager after exceeding the defined number of approval notifications. The data manager can then grant an exceptional approval and commit the request.
2. The request is escalated to an application owner, who changes the approval policy to require fewer approvers, at which point the request is committed: This option is correct because when there are not enough approvers available to satisfy the terms of the approval policy, the request is escalated to an application owner after exceeding the defined number of approval notifications. The application owner can then change the approval policy to require fewer approvers, and then approve and commit the request.
Reference:
https://docs.oracle.com/en/cloud/saas/enterprise-data-management-cloud/edmra/approving-and-enriching-requests.html

The restartService command restarts the services on an environment. This command is useful when you want to refresh an environment after performing maintenance tasks such as importing or exporting snapshots or uploading files. Reference: Using EPM Automate Commands - Oracle Help Center2

In a maintenance view for mappings, you can compare the source and mapping viewpoints to identify nodes that exist in the source but have not been mapped to the target. The next step to define mappings is to create a request, then drag and drop nodes from the source to the mapping viewpoint. This way, you can create new nodes in the mapping viewpoint that have properties derived or transformed from the source nodes using the node type converter and map binding. You do not need to use an Excel mapping file, run a mapping utility, or open a request and add nodes to the target viewpoint, because these are not supported methods for defining mappings in Oracle Enterprise Data Management Cloud. Reference: Working with Requests - Oracle Help Center3; Creating Mapping Viewpoints - Oracle Help Center2

A list viewpoint is a viewpoint that contains only one node type and one node set. A list viewpoint does not contain any hierarchy sets or properties. A list viewpoint is used to manage flat lists of nodes without parent-child relationships or hierarchies. A list viewpoint is related to a dimension through its node type and node set. Reference: Working with List Viewpoints - Oracle Help Center3