How to setup a persistent backdoor on Android?

Its funny, you guys are trying/doing the hacking and im trying to learn how to reverse the remote hack…i know that whoever got me, they are REALLY good. Using the Google Play Services platform to remote install apps to my device, manage my Verizon account(and not through My Account) divert texts, mirror my IMEI, ICCID and then disable my access to calls/text network. Control my device screen remotely and monitor use, not only did they install the apps, but they configured them as hidden system apps with gray buttons. The worst part? They modified my Settings App to prevent Search, Network, Permissions Access and Notification Access. I really need help. Its definitely a challenge.