So I am implementing remove ads function in my app.  

When user clicks remove ads, I first check if already purchased via: 

```
[[SKPaymentQueue defaultQueue] restoreCompletedTransactions];

```

And if so I save a variable in `NSUSerDefaults`, if not user will make a new payment. 

If a user enter an Apple ID who already purchased this (like his friend or something), my variable in `NSUserDefaults` will get changed and ads will be removed on his device. 

My question is: Is that how it's done for all users or am I missing something ?
And can a user access the `NSUserDefaults` like editing a `.plist` file or something ?

Thank you all.