iOS 10.3 is released see if your iPhone is compatible for the upgrade or NOT

iOS 10  compatible iPhones and iPads list

iPhones:

    The iPhone 6s
    The iPhone 6s Plus
    The iPhone 6
    The iPhone 6 Plus
    The iPhone SE
    The iPhone 5S
    The iPhone 5C
    The iPhone 5

iPads:

    iPad Pro 12.9-inch
    iPad Pro 9.7-inch
    The iPad Air 2
    iPad Air
    iPad 4th generation
    The iPad Mini 4
    The iPad Mini 3
    The iPad Mini 2

iPod:

    The iPod Touch 6th-generation

iOS 10 NOT compatible iPhones and iPads list

    The iPad with Retina Display (3rd Gen) and older 9.7-inch iPads
    The iPad Mini
    The iPod Touch 5th-generation and older iPod Touch models
    The iPhone 4S and older iPhone models