iOS7
Features are subject to change. Not all features are available on all devices
Panorama format is available on
iPhone 4S, iPhone 5, and iPod touch (5th generation). Square and video formats and swipe to capture are available on iPhone 4 or later,
iPad (3rd generation or later), iPad mini, and iPod touch (5th generation).
[color=#000000;]Filters in Camera are available on iPhone 5 and iPod touch (5th generation).[/color] Filters in Photos are available on iPhone 4 or later, iPad (3rd generation or later), iPad mini, and iPod touch (5th generation).
AirDrop is available on iPhone 5, iPad (4th generation), iPad mini, and iPod touch (5th generation) and requires an iCloud account.
Siri is available on iPhone 4S, iPhone 5, iPad with Retina display, iPad mini, and iPod touch (5th generation) and requires Internet access. Siri may not be available in all languages or in all areas, and features may vary by area. Cellular data charges may apply. New female and male voices will be available initially in U.S. English, French, and German.
Find My iPhone enables you to locate iOS devices only when they are on and connected to a registered Wi-Fi network or have an active data plan. Some features may not be available for all countries or all areas.
iCloud requires iOS 5 or later on iPhone 3GS or later, iPod touch (3rd generation or later), iPad, or iPad mini; a
Mac computer with OS X Lion or later; or a PC with
Windows 7 or Windows 8 (Outlook 2007 or later or an up-to-date browser is required for accessing email, contacts, and calendars). Some features require iOS 7 and OS X Mavericks. Some features require a Wi-Fi connection. Some features are not available in all countries. Access to some services is limited to 10 devices.
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They could have easily given these underlined features to iPhone 4S as well. I can't seem to find any technological reasons behind omission of them. Variable 1 GHZ A5 SoC & Imagination Technologies PowerVR SGX543 GPU can swiftly take the load of live camera filters without a slouch. And 4S does have the Bluetooth 4.0 hence Airdrop can work on the legacy predecessor as well.
It's just that
Apple giveth & Apple taketh away.