@ComponentScan with multiple configuration class : Annotation Based Configuration

For your Question 1 -

yes, you can register a bean using @ComponentScan in any of the configuration bean which is registered in spring container.you can register a bean into container by any of the following way-

1. Use @Configuration to register bean in rootcontext or dispatchersevletcontext.
2. Import a class in any @Configuration bean (which is already registered in container).

Let say- you have MvcConfig class in which you are scanning component-

@ComponentScan(basePackages = {"xxxx","yyyy","zzzz"})
@Configuration
public class MvcConfig  {
....
}

To register MvcConfig in container you must do-

Either

new AnnotationConfigWebApplicationContext().register(MvcConfig.class);

Or

new AnnotationConfigWebApplicationContext().register(AnotherConfig.class);

@Configuration
@Import({MvcConfig.class})
public class AnotherConfig  {
....
}

For your Question 2 -

Here spring is not only registering MyConfiguration.class but also all the component classes those are present in the package in which MyConfiguration defined.