I just did not understand how it happened. But after upgrading to IOS 6, my friend got Siri on his iPad 2.
Siri is not available on the iPad 2, it's only on the iPad 3+. Are you sure that your friend has an iPad 2 ?
Not possible on iPad 2.
Compare iPad Specs http://www.apple.com/ipad/compare/
iOS 6: Which software features does my iPhone, iPad, or iPod touch support?
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