Okay, sounds to me like your friend wants to totally prevent search engines while at the same time allowing most websites. In other words, no Google, no Bing, no Yahoo, no Baidu, no AOL, no Ask.com, and the list could go on and on.
If my understanding is right, then the best option to cover all bases would be to do as follows:
- Go to Settings
- Tap General
- Tap on Spotlight Search
- Disable Siri Suggestions, Suggestions in Search, Suggestions in Look Up
- Exit Spotlight Search
- Exit General
- Tap on Siri
- Either disable Siri totally OR disable Access on Lock Screen
- Exit Siri
- Tap on General
- Tap on Restrictions
- Enter a restrictions passcode
- Swipe up until you see the list of ALLOWED CONTENT options
- Tap on Websites
- Tap on Limit Adult Content
- Tap on Add a website... under the NEVER ALLOW heading
- Enter google.com and tap Done
- Repeat step 17 for any other search engines he wants to restrict
- Exit Websites and return to the main Restrictions screen
- Swipe down to see the top of the screen
- Disable Siri & Dictation
- Exit Restrictions
Now, the above is total overkill, but should do what he wants. He can then go back and re-enable certain things if this is disabling more than he wanted.
[UPDATE]
In newer versions of iOS, the various Siri options at Step 4 are now located at Settings > Siri & Search.