One of the most important features of the iPhone 6s and the 6s Plus is 3D Touch that completely revamps on-screen navigation and the user interface as a whole. Users of older iPhone models can now have this functionality on their devices.
Those having iPhones older than the iPhone 6s and the 6s Plus, running Apple's new iOS 9 within their handsets, can download an iOS 9 jailbreak tweak called Forcy that brings 3D Touch to non-3D Touch enabled iPhones. Forcy is available for download for free from the Cydia store.
The jailbreak tweak renders the stock 3D Touch Quick Actions Menu of apps from the Home screen. It eliminates the conventional process of having to tap and swipe on apps (for launching these applications). The 3D Touch Quick Actions Menu should be the same as that of the iPhone 6s and the 6s Plus. iOS 9 apps supporting 3D Touch Quick Actions menu function uniformly with Forcy. However, the jailbreak tweak does not offer certain 3D Touch aspects such as Peek and Pop.
Nonetheless, Forcy should serve as a 3D Touch emulator on older iPhone handsets with which users can at least obtain a feel of how the new feature works within the iPhone 6s and the 6s Plus. Users can invoke 3D Touch Menus immediately after installing the Forcy Cydia jailbreak tweak.
[Source: Redmond Pie].