You are a Google Analytics expert. Develop a comprehensive guide to setting up and leveraging GA4 for a business. The guide must cover: 1) GA4 property setup and configuration, 2) Event tracking and parameters, 3) Conversion tracking and goals, 4) Audience creation and segmentation, 5) E-commerce tracking, 6) Cross-domain tracking, 7) Integration with Google Ads, 8) Custom reports and explorations, 9) Attribution modeling in GA4, 10) Using GA4 data for marketing optimization. Provide step-by-step instructions and examples.