React Native is a mobile app development framework that allows developers to build mobile applications using JavaScript and React. It is a separate technology from React, which is a JavaScript library for building user interfaces on the web. While both React and React Native use a similar programming model, they have different APIs and are optimized for different platforms.

In React, the super() constructor with props argument is used to initialize the component's props and state. It is required when defining a constructor in a class component, and should always be called before accessing this.props or this.state.

Styled components are a library for creating React components with embedded styles. They allow you to define styles directly in your JavaScript code using tagged template literals, which makes it easy to style your components based on props and state. Styled components also provide a number of other features, such as server-side rendering, theming, and global styles.

To access the Redux store outside of a component, you can use the getState() method provided by the Redux store. This allows you to access the current state of the store and is often used in middleware or in other parts of the application that do not have direct access to the store.

In React, you can make an AJAX call by using the "fetch" API or a library like Axios or jQuery. The recommended lifecycle method to make an AJAX call is "componentDidMount()", which is called once the component has been mounted to the DOM. This method is a good place to fetch data from an API or server, and update the component state with the new data.

Relay is a library for handling data fetching and caching in React applications. It is often used in conjunction with GraphQL APIs. While Redux is a state management library, Relay focuses specifically on data fetching and caching. Relay provides a number of features, such as declarative data requirements, automatic query generation, and optimistic updates.

TestRenderer is a package that allows developers to render React components to a JSON format, making it easier to test and debug components. It is used for snapshot testing and is similar to the ReactTestUtils package.

Uncaught errors in React 16 and later versions trigger a fatal error and crash the application. This behavior was introduced in order to prevent subtle bugs and inconsistencies that could result from errors being silently ignored or logged to the console.

Concurrent Rendering is a new rendering strategy introduced in React 18 that allows multiple parts of a component tree to be rendered at the same time, without blocking the UI thread. This means that the user interface can remain responsive while React is rendering updates. Concurrent Rendering is particularly useful for large and complex applications that need to maintain high performance.

A parameter can be passed to an event handler or callback in React by using an arrow function. The arrow function takes the event as a parameter, along with any additional parameters that need to be passed. This approach ensures that the event object is properly handled and that the correct parameters are passed to the event handler or callback.