You can use the restrictions feature on the iPhone and iPad to block out all kinds of content that may be inappropriate for small children. If you want to filter out content based on its rating, you'll want to be sure that the correct region is selected for your country. This way you know that the ratings information is accurate. Once you've enabled restrictions, it's as easy as telling parental controls where you're located.
How to choose a rating region for use with iPhone and iPad parental controls
Launch the Settings app on your iPhone or iPad.
Tap on General.
Tap on Restrictions.
Tap on Enable Restrictions at the top if they aren't already enabled. If they are, you can skip to step 6.
Pick a 4-digit passcode that only you will know. Your child should never know this code.
Under the Allowed Content section, tap on Ratings For.
Tap on your country or region name.
That's it. Parental controls and restrictions will remember your selection and when content is filtered out, it will go by ratings standards in your home country.