The default behavior for how the Salesforce B2B Commerce Global APIs transform Salesforce data is to return field names with a lowercase first letter, camelcase convention. For example, the field name ccrz__E_Product__c in Salesforce will be transformed to eProduct in the API. This is done to follow the JavaScript naming convention and to avoid conflicts with the standard Salesforce fields and relationships. Salesforce Reference: B2B Commerce and D2C Commerce Developer Guide, Query Transformation

To check user permissions in Lightning web components, a developer should import two scoped modules: @salesforce/permission and @salesforce/customPermission. The @salesforce/permission module allows the developer to check if the user has access to a standard permission, such as View Setup or Modify All Data. The @salesforce/customPermission module allows the developer to check if the user has access to a custom permission, such as Enable Debug Mode or Manage Orders. The other modules do not exist or are not related to user permissions. Salesforce Reference: Lightning Web Components Developer Guide: Check User Permissions, Lightning Web Components Developer Guide: Import Salesforce Modules

Explanation
To introduce new screen behavior in a checkout flow step, a developer should clone the appropriate subflow and replace the Lightning web components in it. A subflow is a reusable flow that can be invoked from another flow as an element. A checkout flow is a flow that defines the steps and components for the checkout process in the storefront. A checkout flow consists of several subflows, each of which corresponds to a checkout step, such as Cart, Shipping Address, Payment, or Order Summary. To introduce new screen behavior in a checkout flow step, a developer should clone the subflow that matches the checkout step they want to modify and replace the Lightning web components in the cloned subflow with their custom components. The developer can then update the checkoutSteps.xml file to point to the cloned subflow instead of the original subflow. Modifying the property mappings in checkoutSteps.xml is not a valid way to introduce new screen behavior in a checkout flow step, as it only affects how data is passed between subflows, not how screens are displayed or rendered. Editing the default subflow directly is not a valid way either, as it can cause conflicts or errors with other stores or environments that use the same default subflow. Adjusting next-state in previous subflow configuration is not a valid way either, as it only affects how subflows are transitioned or navigated, not how screens are displayed or rendered. Salesforce References: B2B Commerce Developer Guide: Checkout Flow, B2B Commerce Developer Guide: Checkout Subflows, B2B Commerce Developer Guide: Customize Checkout Steps

To enable the ability to add new shipping and billing addresses during checkout, a developer should enable Buyer Managed Contact Point Addresses within the Shipping Address standard component in the Checkout subflow. The Buyer Managed Contact Point Addresses is a feature that allows customers to add, edit, or delete their shipping and billing addresses during checkout. The developer can enable this feature by setting the buyerManagedContactPointAddressesEnabled attribute to true in the Shipping Address standard component in the Checkout subflow. The Shipping Address standard component is a component that displays and collects the shipping address information for the cart or order. The Checkout subflow is a subflow that defines the steps and components for the checkout process in the storefront. Creating a new shipping address checkout subflow that utilizes the Buyer Managed Contact Point Addresses component is not a valid way to enable this feature, as there is no such component as Buyer Managed Contact Point Addresses. Enabling Buyer Managed Contact Point Addresses within Commerce Administration is not a valid way either, as this feature is not configurable in Commerce Administration. Creating a Lightning web component that enables this functionality and replaces the current shipping address screen within the Checkout subflow is not a valid way either, as this is unnecessary and complicated when there is already a standard component that supports this feature. Salesforce Reference: [B2B Commerce Developer Guide: Buyer Managed Contact Point Addresses], [B2B Commerce Developer Guide: Shipping Address Component], [B2B Commerce Developer Guide: Checkout Subflow]