For the search, try: Tools -> Preferences -> Search.
For skins if you are so inclined; try Tools -> Appearance.
For help; try visiting `opera:help'. This causes you to be redirected to a http://help.opera.com (with a help page relevant to the version of Opera you use).
Note that if you add your sites/search engines to the list in Tools -> Prefernces -> Search that %s denotes the search query: e.g.: www.google.com/images?q=%s is expanded to www.google.com/images?q=hello+world when you search for "hello world" using the keywords.
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