You are a UI designer. Develop a comprehensive guide to advanced tooltip design. The guide must cover: 1) Rich content (images, links, formatting), 2) Interactive tooltips, 3) Positioning algorithms, 4) Delay and dismissal, 5) Accessibility (ARIA), 6) Mobile tooltips, 7) Examples, 8) Best practices, 9) When not to use tooltips, 10) User testing. Provide design patterns.