Explanation
The data source that is needed when using the TypeAhead element is DataRaptor Extract Action. A TypeAhead element is an element that can display a list of suggestions for the user to select from, as they type in a text field. A DataRaptor Extract Action is an action that can retrieve data from a Salesforce object or invoke a Salesforce API, using SOQL queries or Apex methods. The consultant can use a DataRaptor Extract Action as a data source for the TypeAhead element, to get the contact names from Salesforce and display them as suggestions

A record locking error normally indicates concurrent update contention: two or more transactions are trying to modify the same Salesforce record, or related locked records, at the same time. During a Data Mapper Load, this can happen when multiple users, automations, batch jobs, integrations, or OmniStudio processes attempt to update the same parent or child record concurrently. It is not primarily a field-level security issue; permission failures produce authorization errors. It also does not automatically mean the record is being archived or that the object batch size has been exceeded. The fix is usually architectural: reduce concurrent writes to the same record, serialize critical updates, review automation on the object, and avoid unnecessary parent-record updates. Salesforce documents UNABLE_TO_LOCK_ROW style behavior as a concurrent update/record lock problem.

Below is the formatted question with a 100% verified answer based on official Salesforce OmniStudio documentation, including a comprehensive explanation and references.

In OmniScript, pages or groups of fields can be controlled based on the choices made by the user by using the Conditional View property on a Step or Block element. A Conditional View property is a property that determines whether a Step or Block element is displayed or hidden based on certain criteria, such as data values or user roles. The consultant can use the Conditional View property to show or hide different pages or groups of fields in the OmniScript depending on the user's input

The OmniScript feature that should be recommended to meet this requirement is Conditional Views.
Conditional Views allow the designer to create different paths within an OmniScript based on user responses or data values. User Roles are used to control access and visibility of OmniScripts based on user profiles or permissions. Script Configuration is used to define general settings and properties of an OmniScript. Script Profiles are used to assign different versions of an OmniScript to different user groups.