I am using inline_create for tag model while creating question. inline creating is woking well. But, the tag selection input box throws an error The route admin/question/fetch/tags could not be found., when I start type in tag selection box.
Finally, it was solved.
I have added, \Backpack\CRUD\app\Http\Controllers\Operations\FetchOperation;
trait to my Question Crud Controller. It works well.
Now, I think, documentation should get more enhanced.