The Forcy app emulates one of the main features of the 3D Touch, creating instant shortcuts for apps by touching them with a finger
If you do not want to buy an iPhone 6s, but you would like it too 3D Touch, well: you can have something similar on "old" iOS 9 models thanks to the Forcy app, available for free on Cydia, the free store that allows you to install apps that aren't on the official Apple store. Which means having an iPhone with jailbreak, an operation that must be evaluated very carefully before making it.
Obviously the final result is not identical, because the true 3D Touch is based on a specific hardware placed under the screen and there is no way to really emulate it via software no haptic feedback, for example. However, Forcy adds a very similar function to that of the 3D Touch: touching the icon of an app with a movement of the finger upwards a quick menu is activated with various shortcuts, which allow access to the flight to specific actions of the app. It won't be like having an iPhone 6s in your hand, but how much closer you can get.