If you downloaded 「ROM: Golden Age」 through Google Play Store, you can set up a payment password to prevent accidental purchases.

[How to Set Up Google Play Store Payment Password]
1. Launch Google Play Store and Tap profile picture next to search bar
2. Settings > User Controls > Require Authentication for Purchases
3. Select 'Require authentication for all purchases through Google Play on this device'
4. Set up payment password for Google account