Apple - Reset Safari from command line
From http://seanscus.blogspot.com/2012/08/completely-reset-safari.html
Open a terminal and enter the following commands to fully wipe out all of your old Safari settings:
mv ~/Library/Safari ~/Desktop/Safari-`date +%Y%m%d%H%M%S`; \
rm -Rf ~/Library/Caches/Apple\ -\ Safari\ -\ Safari\ Extensions\ Gallery; \
rm -Rf ~/Library/Caches/Metadata/Safari; \
rm -Rf ~/Library/Caches/com.apple.Safari; \
rm -Rf ~/Library/Caches/com.apple.WebKit.PluginProcess; \
rm -Rf ~/Library/Cookies/Cookies.binarycookies; \
rm -Rf ~/Library/Preferences/Apple\ -\ Safari\ -\ Safari\ Extensions\ Gallery; \
rm -Rf ~/Library/Preferences/com.apple.Safari.LSSharedFileList.plist; \
rm -Rf ~/Library/Preferences/com.apple.Safari.RSS.plist; \
rm -Rf ~/Library/Preferences/com.apple.Safari.plist; \
rm -Rf ~/Library/Preferences/com.apple.WebFoundation.plist; \
rm -Rf ~/Library/Preferences/com.apple.WebKit.PluginHost.plist; \
rm -Rf ~/Library/Preferences/com.apple.WebKit.PluginProcess.plist; \
rm -Rf ~/Library/PubSub/Database; \
rm -Rf ~/Library/Saved\ Application\ State/com.apple.Safari.savedState
Oh, my! Just press and hold Shift when launching Safari from the dock.
But you have got in answers above exactly what you have asked for)
Disconnect your computer from the internet (disable wlan) Then delete browser history (Safari/Preferences/Privacy: remove all website data)