The project.json file was used in ASP.NET Core 1.0, but it was replaced with a different project file format starting from ASP.NET Core 2.0.

To enable MVC in ASP.NET Core, you should invoke the services.AddMvc() method inside the ConfigureServices method of the Startup.cs class. This method configures MVC services, such as routing, controllers, and view engines, making MVC available in your application.

You can pass data from a controller to a Razor view using multiple techniques, including ViewBag, ViewData, and TempData. These options allow you to share data between a controller and a view, but they have different lifetimes and use cases.

To extend the default user store in ASP.NET Core Identity, you would typically implement the IUserStore interface. This interface allows you to customize how user information is stored and managed. You can create a custom user store by implementing this interface and providing your own data storage mechanisms.

To prevent integration tests from impacting the actual database, an in-memory database is often used. It simulates database behavior but operates entirely in memory, making tests faster and isolated. It's a common practice in ASP.NET Core testing.

One of the major advantages of ASP.NET Core is its ability to run on multiple platforms, including Windows, Linux, and macOS. This cross-platform compatibility provides greater flexibility in choosing the hosting environment for your ASP.NET Core applications.

When configuring ASP.NET Core Identity, the 'IdentityOptions' class is used to specify various settings, including policies like password strength and lockout duration. This class allows fine-grained control over the behavior of Identity.

The UseDefaultFiles middleware is used to serve default files, like index.html, when a user accesses the root URL of a web application. This middleware ensures that the SPA's default page is served correctly. Make sure to include app.UseDefaultFiles(); in your Configure method.

In ASP.NET Core Identity, the UserManager class is primarily responsible for user management, including creating users. It provides a set of methods to perform user-related operations, such as creating, updating, deleting, and finding users.

Azure App Service is a Platform-as-a-Service (PaaS) offering that simplifies the deployment and scaling of web applications. It supports auto-scaling based on demand and allows you to easily configure custom domains, making it a suitable choice for hosting ASP.NET Core applications on Azure.