Google-search – O Google, where art thou Linux special search

I don't know about the technical details of the implementation of those other sites. However, if there are sites that don't use account or cookie prefs to know what you normally search, I would expect nothing less than different results.

Google has been personalizing search results for years to give you information tailored to your needs. Recently, Google search results have been more explicit, displaying search results based on what people in your friend network work have shared. Also, see ratings and reviews on Google Places, for example, where your ratings and those of your friends modify your results giving you better, more personalized information.

For looking through your visited pages, I couldn't find any feature other than some chrome extensions that showed the most visited pages on google.

Example of some plugins that do this: Most Visited, Recent History...

You can also try looking at the google archives to see previous versions of google and copy the code or something,

Other than that for visited pages, you can easily search through the closed tabs/history page,

But not all visited pages, just most visited and history...

Regarding the reading level feature, you can see the archive file here, but there are also some chrome exertions that have some aspects of that feature. Depending on why you wanted it there are alternatives.

That's all I know about those features, hopefully it could help a little.