I got my nexus 4 about 2 years ago (times goes very fast). It came with Android 4.2 and is upgraded in several steps till 5.1. Always OTA. I also have installed and uninstalled apps. And finally I decided to do a factory reset (what I never did before).
My plan was:
- export configuration and data for all application which support this to a local storage (mostly all I use do)
- prepare the list of apps I have installed
- copy all files from internal storage to a computer
- do factory reset
- configure my google account
- reinstall apps
- import configs and data
- move some files back to the phone storage, only files I do know.
The first surprise I met in step 3, I'll describe this in a separate post, but the fact is that many files not visible if phone is connected to PC with a usb cable. Finally I have to copy files via network what was a bit slower.
The next funny issue I met on step 4. I use 2 factory authentication. Therefore when I was configuring my google account after reset, I need to enter one time code google sent me by sms. But I could not get the sms since the phone was not fully "activated". To read an SMS I need to activate a phone, to activate a phone I need the sms. Deadlock. Actually, I guess one can do activate google account later on, but I decided to do this first. I used one of the emergency "offline" codes google gives for 2 factory authentication.
Afterwards, google automatically suggested me to restore apps I had on my phone before reset. What means I could skip step 2.
Afterward, I did all as planned - worked fine. I did not loose any important data and have refreshed (and cleaned up) smartphone.