The Automated Test Framework (ATF) is a tool that allows you to create and run automated tests on the ServiceNow platform. The ATF uses test steps to define the actions and validations for each test. The test step that allows you to create a user with specified roles and groups for the test is the Create a user test step. This test step creates a temporary user record that is deleted at the end of the test. You can specify the user name, password, roles, and groups for the user. You can also use the Impersonate a user test step to switch to the created user and perform actions as that user.
The other options are not valid test steps for creating a user. The Create a role and Create a group test steps do not exist in the ATF. To create a role or a group, you need to use the Create a record test step and specify the sys_user_role or sys_user_group table. The Impersonation test step does not create a user, but switches to an existing user.
References:
[Automated Test Framework overview]
[Automated Test Framework test steps]
[Create a user test step]
[Impersonate a user test step]

A Display Business Rule has access to the current, g_scratchpad, and GlideSystem objects, but not the previous object. The previous object is only available to Before Business Rules4. References: Business Rule API
https://docs.servicenow.com/bundle/tokyo-application-development/page/script/business-rules/concept/c_Busine

One of the uses of the ServiceNow REST API Explorer is to create sample code for sending REST requests to ServiceNow. The REST API Explorer is a tool that allows you to discover and test the ServiceNow REST APIs. You can select an API endpoint, set the HTTP method, parameters, headers, and body, and then execute the request. The REST API Explorer will show you the response status, headers, and body, as well as generate sample code for various languages and frameworks, such as cURL, Java, JavaScript, Node.js, Python, Ruby, and more. References: [Use the REST API Explorer - Product Documentation: Tokyo - ServiceNow],
[Introduction to Scripted REST APIs - ServiceNow Developers]