Tap New pass, then scan the barcode, pick a photo or screenshot, or type the number. Style it and tap Add to Apple Wallet.
Open the pass in Carddrop, go to Barcode and check the format matches your card (the app warns about wrong check digits). The number is always shown so the cashier can type it in.
Some tickets use codes that change every few seconds. A copy can't reproduce those; use the organiser's own app for them.
Settings → Restore purchases, signed in with the same Apple Account you bought with. Manage or cancel subscriptions in your iPhone's Settings → your name → Subscriptions.
Yes. See the privacy policy.