To ensure users can view their booked tickets offline in a PWA, the best approach is to implement Service Workers (option b). Service Workers can intercept network requests, cache ticket data, and serve it to users when they are offline. Local storage (option a) is limited in capacity and may not provide a seamless offline experience. Downloading PDFs (option c) is not user-friendly, and cookies (option d) are not suitable for storing large amounts of data offline.

The primary benefit of using the Context API in React is global state management. Context API allows you to create a global state that can be accessed by multiple components, eliminating the need to pass props through multiple levels of components. While it may help reduce re-renders in some cases, its primary advantage is its ability to manage global state.

In this scenario, the most suitable advanced React pattern would be Portals. Portals allow you to render a component outside the normal DOM hierarchy while maintaining control over it from within a component. This is especially useful for scenarios like modals, tooltips, or popovers that need to be rendered outside the parent DOM tree. Context API, Render Props, and Redux are useful in different contexts but not specifically designed for this scenario.

To ensure that actual API calls are not made during test runs, you can use a mocking library like Jest's jest.mock to mock the API calls. This allows you to replace the real API calls with mocked responses, enabling controlled and predictable testing without hitting external services. Manually disabling the network connection or deploying to a staging environment is not practical or recommended for unit testing. Rewriting API calls to return fake data can be done through mocking, which is a more effective approach.

When you need to render a child component into a different DOM node, outside of the parent DOM hierarchy, React Portals are the appropriate choice. They act as a bridge or gateway to render content in a different place in the DOM while maintaining React's component structure and functionality.

To ensure that a modal renders directly under the body tag and is not affected by parent CSS, you should use React Portals. Portals allow you to render a component at a different DOM location, making it appear outside the DOM hierarchy of parent containers, thus avoiding any CSS interference. This is commonly used for modals and overlays.

The best approach to prevent a specific widget's failure from crashing the entire app is to wrap that widget component with a try-catch block. This way, exceptions occurring in that widget won't propagate up and crash the entire app. Global error boundaries (Option 1) are useful but may not be fine-grained enough to handle specific widget failures. Modifying the third-party library (Option 3) is not always possible or practical, and "window.onerror" (Option 4) is a global event handler, which may not be specific enough.

When animating route transitions in React, the transition state can be used to manage custom animations between routes. The transition state is part of the React Transition Group library and provides a way to handle animations during route transitions. This state allows developers to control how components enter and exit the DOM during navigation transitions.

In Redux, the tool or mechanism that intercepts every action before it reaches the reducer is known as "ReduxMiddleware." Middleware allows you to perform additional actions, such as logging, asynchronous operations, or modifying the action itself, before it reaches the reducer. It's a key part of extending Redux's functionality.

Render Props leverage the power of closures in JavaScript to achieve their functionality. Closures allow a function to maintain access to variables from its containing scope even after that scope has exited. This enables the Render Props pattern to encapsulate and share behavior effectively, making it a versatile tool in component design.