To turn off in-app purchasing for iOS, do the following:
- Go to Settings and then General.
- Scroll about halfway down the page and tap Restrictions
- Tap Enable Restrictions
- Enter a 4-digit password that locks certain functions of the device. Use a passcode that isn't the same as the passcode used for the device (if the kid knows it).
- Once the passcode is set, scroll down to the second set of options. Slide the In-App Purchases slider to Off (in iOS 6) or to the left so that it's white (iOS 7 and up). This will prevent anyone who doesn't know your passcode from making purchases.
- If you change your mind and later want to restore the ability to make in-app purchases, simply come back to this screen and change the position of the slider.
- Open the Google Play store.
- Tap menu button. On most phones this is the set of lines in the upper left corner of the screen.
- Tap Settings.
- Tap “Require password for purchases.” By default Android is set to request a password for purchases made 30 minutes apart or more.
- Tap “For all purchases through Google Play on this device.” This will also stop Junior from downloading new apps without your password.