Your key was shown once on the page right after checkout. Lost it? Open your account page (the link in that same page, or your checkout receipt path) and choose rotate — a fresh key is issued and the old one stops working immediately.
Payments, renewals, and cancellations run through Stripe under the plan you picked at checkout. When a subscription ends, your entitlement switches off automatically.
Your answers live in your browser on your device. Clearing browser data clears the checkup. The app works offline after the first visit; choose “Install this app” (or Add to Home Screen) to keep it on your phone.
Fastest path: message @jussnco on Instagram. For anything account-specific, be ready to confirm the email you enrolled with.