Develop a comprehensive blueprint for a User-Generated Content (UGC) campaign.  This blueprint should be structured as a chain prompt, guiding the user through each stage of the process.  The first prompt should focus on defining clear campaign goals and target audience. Subsequent prompts will build upon this foundation, covering aspects such as content theme selection, platform strategy (e.g., TikTok, Instagram, YouTube), incentive structure (e.g., prizes, affiliate commissions), content guidelines, community engagement strategy, measurement and reporting, and potential legal considerations. Each stage should be detailed with actionable steps, best practices, and relevant examples.  The final prompt should synthesize all previous steps into a concise, actionable campaign plan, including a timeline and budget allocation.  Assume the campaign targets a younger demographic (18-35) interested in sustainable fashion.  The output should be formatted as a numbered list, with each number representing a stage in the campaign blueprint, and detailed instructions and examples for each stage. The final output should also include a sample marketing calendar and a list of key performance indicators (KPIs) to track campaign success.