An input control is a type of filter that allows you to dynamically change the values of dimensions or measures in your story or application. You can use an input control to filter dimension or measure values and select dimension or measure values for your widgets, such as charts, tables, or geo maps1. For example, you can create an input control that lets you choose which product category or year to display in your chart2.
You cannot use an input control to define a prompt or explore data relationships. A prompt is a filter that is applied to a model before the data is loaded into a story or an application. Prompts allow you to select the data that you want to see in your story or application. You can create prompts in the modeler, not in the story or application3. To explore data relationships, you can use the Smart Discovery feature, which allows you to automatically generate insights and visualizations based on your dat a. You can access Smart Discovery from the context menu of a chart or table widget4.

Datapoint comments are stored in the data model, not in the widget, page, or story. This means that datapoint comments are visible across different stories that use the same model, and they are preserved when a story is duplicated or exported. Verified Reference: [SAP Analytics Cloud - Datapoint Comments]

The Optimized Design Experience is a new user interface for SAP Analytics Cloud that simplifies and enhances the story design process. The Optimized Design Experience introduces some new elements and tools, such as Data Analyzer, Point of Interest, Time Series chart, etc. However, it also removes some elements and tools that are available in the Classic Design Experience, such as Grid page, Explorer, Digital Boardroom, etc. Therefore, the correct answer is Grid page, as it is the element that is not available in the Optimized Design Experience.