IOS – How to enable “Siri Knowledge” suggestion in Safari

It looks like it's indeed a hole in iphone's safari. I'm not sure if it was always like that or if it's a new undocumented feature that might soon go away.

But meanwhile you can try using Inspell if you're willing to jailbreak. There's just no other way to fix such an issue: it's either apple or cydia.

Another option, if the error occured only in safari, is using another browser. But that doesn't seem to be this case.

I'm not completely sure, but I think that's just a feature of Google's mobile site. I don't know that there's a way to enable it in the Google Search App. Perhaps they will add this feature down the road. I'll edit my answer if I find it is possible.