Loadable components are a way to load other components asynchronously in React. Loadable components allow components to be split into smaller chunks and loaded on-demand, improving performance and reducing initial load times. Loadable components are typically used with dynamic imports to enable asynchronous loading of code.

Higher-Order components (HOCs) are components that enhance the behavior of other components by adding additional functionality or props. HOCs take a component as input and return a new component that includes the additional behavior. This allows developers to reuse code and separate concerns in their applications.

redux-saga is a middleware library for Redux that allows you to handle side effects, such as asynchronous data fetching or complex state updates, in a declarative and testable way. It uses ES6 Generators to provide a more readable and maintainable way to handle complex logic in your Redux application.

Forward refs are a way to pass a ref from a parent component to a child component. This allows the parent component to access and manipulate the child component's DOM node. Forward refs are created using the React.forwardRef() function.

It is not mandatory to define a constructor for a React component. If the component does not need to set its initial state or bind methods to the component, the constructor can be omitted. Additionally, if the component does not have any props, a constructor is not necessary.

In React, component names should start with a capital letter in order to distinguish them from regular HTML tags and make the code easier to read. This is a convention that is widely used in the React community and helps developers understand the purpose and scope of different parts of the code.

To set state with a dynamic key name, you can use the setState() method with a variable key name. This allows you to create new state keys based on user input or other dynamic data.

React components use composition rather than inheritance to build complex UI components. Composition allows components to be composed of multiple smaller components, each with their own logic and behavior. This makes components more reusable and easier to manage than inheritance-based approaches.

The render method of the react-dom package is used to render a React component to the client-side DOM. The render method takes two arguments: the component to render and the DOM element to render it to.

A simple example of a Jest test case would be testing a component's render method. For example, you could test that a component renders a specific HTML element or that it correctly sets a state variable.