Checking the Enable Cancel checkbox in the Setup tab under Cancel Options allows the developer to enable the cancel functionality for all steps in the OmniScript. The user can cancel the OmniScript at any time by clicking the Cancel button in the top right corner of the OmniScript.
Adding a navigation Action inside each step is not necessary and would clutter the OmniScript design. Setting the Component name or Element Name to `'Cancel'' has no effect on enabling the cancel functionality.

According to the OmniScript Action Elements page, a DataRaptor Extract Action can be used to "get data from one or more Salesforce records" and an HTTP Action can be used to "get, save, or delete data through a web application programming interface (API)".

A DataRaptor Turbo Extract is a simplified version of a DataRaptor Extract that can retrieve data from a single object without changing the structure of the output data. It is easier to configure because it does not require defining extraction steps or JSON paths. It also has better performance at runtime because it uses a native query engine instead of a custom one

The Expression Set component in OmniStudio allows developers to perform calculations using steps such as Aggregation, Calculation, and Sub Expression.
C). Add an Aggregation Step as SUM(BasePrice) ?This is correct. Aggregation steps are specifically designed to perform functions like SUM, AVG, COUNT, MIN, MAX over collections (arrays) of data. In this use case, summing the entire BasePrice array is best handled using an Aggregation Step.

Setting the collapsible property on the block element allows the user to expand or collapse the block as needed. Using a Data table element is not suitable for displaying contact information.
Setting the class'' collapsible'' on the block element has no effect. Using a conditional FlexCard State requires a condition to be met, not a user choice.