In Angular, the CanDeactivate Guard checks whether a route can be deactivated, allowing you to confirm or prevent the user's navigation away from the current route.

For debugging and profiling Angular applications, developers can use the Augury browser extension. It provides insights into an Angular app's structure and behavior.

In Protractor, the onPrepare function is used to initialize the browser before tests run, making it suitable for setting up the environment.

The primary purpose of a Route Resolver in Angular is to fetch route parameters and data before navigating to a route.

The best approach to ensure that all components refer to the same instance of a service is to use the 'singleton' pattern, which allows a single instance of the service to be shared among multiple components.

In Angular testing, the trigger function is used to simulate user interactions on elements, such as clicks, inputs, and other events.

The RxJS operator debounceTime is used to delay the emissions from an Observable. It's often used for scenarios like handling user input and performing searches with a delay.

The OnPush strategy in Angular's change detection checks the component and its children only when an event is fired, optimizing performance.

In Angular testing, the **async** utility is used to handle promise-based asynchronous tests, while the **fakeAsync** utility is used for simulating asynchronous operations in a synchronous manner. These utilities help control and test asynchronous behavior effectively in different testing scenarios.

To implement cross-field validation in a reactive form, you would typically define custom validators that check and enforce validation rules involving multiple fields.