Lets say I want to retrieve a file that is about one year old. I have been doing one or two factory resets to this day and kept using my phone. Now I want to get that file back, is it possible to get it?
When you factory-reset your device storage is not wiped but inaccessible (over written with 0's if encrypted).¹ On top of it you have been using your device which means memory is overwritten again by the apps you installed (and their data).
Effectively, your chances of recovering anything is zero unless you want to try extremely sophisticated data recovery means and maybe recover a figment of file, if at all
¹ See for more details here. Also, as Izzy pointed out in a now deleted comment, it's really "overwritten" only if it was encrypted or if the space was reclaimed by the controller (see Wear-Leveling). So there is a chance such a file could be recovered even after multiple factory-resets. Feasibility is a different thing, especially as one cannot mount internal storage to a PC to use forensics software on it, nor (without root access) generate a disk image for doing so. And agreed, chances are not that good anyway ;)