Does Premium transfer between App Store, Google Play, and Steam?

No. App Store, Google Play, and Steam purchases are separate. For example, purchasing on the App Store does not unlock the Google Play or Steam edition.

Switching devices within the same store is a different situation: iPad and iPhone can share an iOS purchase when you use the same purchasing Apple Account.

If you purchased through the App Store or Google Play but Premium is missing, follow Restore Purchase before buying again. Restoring a purchase does not transfer it between stores.

For Steam, make sure you are launching the version installed from your Steam Library. See Steam activation and Library troubleshooting if Resprite is missing or you see trial limits. Steam does not use the App Store or Google Play restore-purchase process.