Explanation
To view the fields available for the Product Detail Page, the developer should type CCRZ.productDetailModel in the Developer Tools Console in the browser. This will display the product detail model object, which contains the product data and attributes that are rendered on the page. The other options are either not valid or not relevant for the Product Detail Page.

The difference between Gross Layout Overrides and Subscriber Templates is that Subscriber Templates allow for modification of the header and the footer, while Gross Layout Overrides allow for modification everything inside the header and footer. Subscriber Templates are custom Visualforce pages that can replace the standard header and footer components on a page. Gross Layout Overrides are custom Visualforce pages that can replace the default layout of a page, such as the number of columns, theposition of widgets, or the content of sections. Salesforce References: B2B Commerce and D2C Commerce Developer Guide, Subscriber Templates, Gross Layout Overrides

To make an integration available for selection in Salesforce B2B Commerce, a developer must create a RegisteredExternalServicerecord. This can be accomplished using tools like Workbench, which allow for direct interaction with Salesforce's backend database. By registering the external service, the integration becomes selectable within the B2B Commerce setup, allowing it to be associated with specific stores or contexts. Salesforce documentation on integrating external services with B2BCommerce provides step-by-step instructions on registering these services to enable seamless integration and functionality within the platform.

Explanation
The ccUtil apex class provides two methods to check the input or return data of the Global API's:
ccrz.ccUtil.isNotEmpty(Map<String, Object>) and ccrz.ccUtil.isEmpty(Map<String, Object>). These methods return true if the map is not null and contains at least one entry, or if the map is null or empty, respectively.
Similarly, ccrz.ccUtil.isNotEmpty(List<Object>) and ccrz.ccUtil.isEmpty(List<Object>) return true if the list is not null and contains at least one element, or if the list is null or empty, respectively. These methods are useful for validating the input parameters or the output results of the Global API's.