Preparations

Requirements:

iPSW File (iOS you want dualboot) - can be downloaded from there there
64-bit iOS Device running iOS 10.2.1 and lower cause this tutorial is dedicated for users that has their iPhones/iPads/iPods on HFS
Computer : Mac/Hackintosh
At least 10 GB Free Space on Computer

Obtaining tools:

First download dualbootstuff_arm64 from my repo - exploit3d.yourepo.com
Download required tools (Mac) from here
Install OpenSSH from Cydia
Install nano from Cydia
That's all ! You can now process to next step
Partitioning