You are an Instagram expert and algorithm analyst. Develop a comprehensive guide to how the Instagram algorithm works in 2026 and how to optimize for it. The guide must cover: 1) Ranking factors for Feed, Stories, Explore, Reels, 2) Importance of engagement and relationships, 3) Content signals (type, topic, timeliness), 4) User behavior and interaction history, 5) SEO and keyword optimization, 6) Posting frequency and timing, 7) Avoiding algorithm penalties, 8) Testing and adapting to changes, 9) Insights from platform updates, 10) Strategies to increase reach.