Razor views in ASP.NET Core are primarily used for creating user interfaces for web applications. They allow developers to define the structure and layout of web pages using a combination of HTML and C# code. Razor views are essential for rendering dynamic content and interacting with server-side data in web applications.

In ASP.NET Core, the order of route definitions significantly impacts the routing process. Routes are executed in the order they are defined, and the first matching route is used to handle the request. This allows developers to control how different routes are prioritized and which controller action or endpoint is invoked based on the request URL.

To create a corresponding backend model for the registration page, you can use Entity Framework Core. Entity Framework Core allows you to define data models that represent database tables, making it easier to work with data in your ASP.NET Core application.

To load related data upfront and avoid additional queries, you should employ "Eager Loading." Eager Loading allows you to retrieve related entities in a single query by specifying what related data to include using the Include method in Entity Framework Core.

To pass data from a controller to a view, you can use a Model object. Models are classes that define the data structure and properties you want to pass to the view. They enable strong typing and are a fundamental part of the Model-View-Controller (MVC) architecture in ASP.NET Core.

To customize authorization logic in ASP.NET Core, you can implement the IAuthorizationFilter interface. This interface allows you to create custom authorization logic that can be applied to controllers and actions. It gives you fine-grained control over how authorization is performed for specific requests.

The "lockout" feature in ASP.NET Core Identity relates to locking user accounts after a certain number of failed login attempts. This is a security measure to protect against brute-force attacks and unauthorized access. When an account is locked, the user cannot log in until the lockout period expires or is manually reset by an administrator.

The .NET SDK includes the .NET runtime, but it also contains development tools, libraries, and compilers required for developing .NET applications. In contrast, the .NET runtime is primarily used for running already developed .NET applications.

In Razor forms, you can use the validation-for Razor tag helper to display validation messages for a specific property. This tag helper generates HTML markup that shows validation messages associated with a model property. It's a handy tool for providing feedback to users when form validation fails for a particular field.

The correct method is AddRouting. This method is used to add and configure the necessary middleware for routing in ASP.NET Core. It's a fundamental step in setting up routing for your web application.