The app is not in the App Store or on Google Play yet, so neither sells passes. An exam bought in the App Store before passes stays yours, under the account you bought it with.
Passes are sold on licento.com for now. Sign in to the app with the same account, and your pass is there.
A purchase in the App Store or on Google Play belongs to the Licento account you were signed in to when you bought it. On a new phone, or after reinstalling the app, sign in with that account and tap «Restore purchases» in Me.
Refunds for those purchases are Apple’s or Google’s. If either refunds one, your access to that exam ends.