A one-person studio — your email comes straight to me.
Tell me which app, which iPhone and which iOS version and I can fix it much faster. A screenshot helps too.
Every app has a "Restore purchase" button in Settings. Make sure you're signed in with the same Apple Account; one-time purchases are permanent.
Because the apps run on device, your data is included in your iPhone backup (iCloud Backup or a computer backup). Restoring a backup on a new phone brings everything along.
Sessiz and Fence use Apple's Screen Time framework. Without that permission iOS won't let any app block another. You can revoke it any time in Settings → Screen Time.
Send it over — the upside of a one-person studio is that suggestions can genuinely land in the next update.