wp-cache not serving and multiple cache file

I’ve been trying to install wp-supercache but not working properly. The installation was smooth. When i try to open the site using other browser (not logged in), the cache was generated but the page is not served from the cache (i checked to source).

When multiple users are accessing the same post, the cache is created for each user. I realized that when i checked the cache content list in admin panel.

I tried to disable and uninstall the plugin and tried wp-cache, same results……..

one more thing, i got this msg too “Mod rewrite is not installed! Super Cache will not fully work!” although the mod_rewrite is installed and working.

so, 3 problems
1. not serving from cache (no super page msg)
2. multiple cache for 1 post
3. mod_rewrite error msg

appreciate your help