My iPhone updated itself overnight and I got a surprise - HELP

Once I woke up and unlocked the device, it looked brand new. It asked me to reconfigure all the settings I had programmed from scratch. Like Face ID, the camera, everything.

Once the update was complete, I had to turn on the phone. It started with the multilingual greetings "hello..." and wouldn't let me do anything. Like it was a toy phone. I tried a quick restart (volume up, volume down, and photo). I restarted it that way and was able to skip all the setup steps. But as I said before, I don't think this should happen since I want all my preferences back the way they were. An additional detail: when trying to restore from iCloud, that option is grayed out. And my Gmail account email has now changed to an older Hotmail account (also mine, but an older one).

I understand that one possibility is to customize everything again. But it's awful, especially since it's a work tool, and I understand that this shouldn't happen to me because of an update.

Please, if anyone knows, I need your help.