WordPress/PHP Backend Developer Needed

I have an existing WordPress website with the front-end design already completed. I need an experienced backend developer to implement the functionality. The project includes a custom WordPress plugin/database, authenticated student area, timed assessments with autosave/recovery, audio recording/upload, question-bank logic, admin dashboard, AI API integration, report generation, Stripe, Cal.com, Brevo and webhook integrations. The workflows, screens and functional specification will be provided — this is primarily an implementation job, not a design/discovery project. You must have proven experience with PHP, WordPress custom plugin development, MySQL, REST/AJAX, authentication/security, APIs and webhooks. Please send examples of custom WordPress systems/plugins you personally built, explain which parts you built yourself, your availability, estimated timeframe and fixed-price estimate. Please do not apply if your experience is mainly Elementor/page design or installing/configuring existing plugins. How many hours do you need to complete these? And how many days in total? What support do you give during testing phase?