In reactive forms, the property that holds the latest validation errors for a form control is called "errors." You can access this property to check for validation errors on a specific form control. It provides information about validation failures, if any. The other options are not the correct property names for holding validation errors in reactive forms.

To enable users to inject custom content for the header, sidebar, and main content area in an Angular layout component, you can use ng-templates with ng-containers to define placeholders. Users can then fill these placeholders with their custom content. This approach provides flexibility and is a common pattern for creating layouts with dynamic content. While other options like directives, dynamic components, and pipes have their use cases, they are not the most suitable choice for this specific scenario.

To allow users to add or remove input fields dynamically, you would typically use the FormArray feature in Angular. FormArray allows you to create arrays of form controls dynamically, making it ideal for scenarios where the number of input fields can change. Reactive Forms provide a more robust way to manage form data compared to Template-driven Forms, and ngFor is a directive used for rendering lists but doesn't handle form controls.

In template-driven forms in Angular, the "ngModel" directive is used to bind an input field to a property in the component's class. This directive establishes two-way data binding between the form control and the component class property, allowing changes in the input field to be reflected in the component and vice versa.

To programmatically navigate to a different route in an Angular application, you should use the 'navigate' method from the 'Router' service. This method allows you to navigate to a specified route by providing the route path or an array of route segments. It's a common approach for handling navigation within Angular components or services.

To send data from a parent component to a child component in Angular, you should use the @Input property decorator. It allows the parent component to bind data to a property of the child component. The other options, such as @ViewChild, @Output, and @ContentChild, serve different purposes, like accessing child elements or emitting events.

To enable strict mode for a new Angular application, which enforces stricter type-checking and other stricter checks, you would use the --strict flag with the ng new command. This flag sets up the project with more rigorous TypeScript checks and helps catch errors at compile-time.

To dynamically render widgets based on user preferences, you would leverage the ngIf structural directive in Angular. This directive conditionally renders or removes elements based on a given expression. It's ideal for showing or hiding widgets as needed without re-rendering the entire component. The other options, such as @ViewChild, ngOnChanges, and ngFor, have different use cases and are not suitable for this specific scenario.

The CanDeactivate route guard is used for scenarios where you want to prompt the user with a confirmation message before navigating away from a route. It's commonly used for guarding forms to prevent users from losing unsaved data.

The primary role of "Effects" in NgRx is to manage side effects in your application. Side effects can include making HTTP requests, interacting with external services, and other asynchronous operations. Effects help keep your reducers pure by handling these tasks separately.