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iOS 11 specifically, as far as I know... none. They're all available including 3D Touch ones through long press.

Yup! 3D Touch features in the Control Center are also available on iPhone 6 via long press. Works the same.
 
Generally the latest version of iOS only includes new features that are exclusive to the correlated new iPhone that year. Sometimes some features are excluded from older/no longer sold devices due to performance issues, but I feel that this is less common as of the past few iOS releases.

Surely iOS 11 will have some not yet unveiled features that only the new 2017 iPhone will have.
 
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