You can't revert to iOS 9. Apple stopped signing that software, so it's impossible to get back to it.
The slide screen was a feature of iOS, until the release of iOS 10. 10.0.1 got rid of the slide, and since you can't revert to a software previous to iOS 10, there's also no option to get the slide screen back.
The iPhone 6 was released in September 2014, the 6s in 2015. The s in 6s simply tells that your device is the model from last year.
The slide screen was a feature of iOS, until the release of iOS 10. 10.0.1 got rid of the slide, and since you can't revert to a software previous to iOS 10, there's also no option to get the slide screen back.
The iPhone 6 was released in September 2014, the 6s in 2015. The s in 6s simply tells that your device is the model from last year.