I use an old phone as a camera for my 3d printer as well. They can also be used to run octopi provided they have otg usb

You can have internet over bluetooth, both as a hotspot and as a tether, maybe that’s the thing?

Not usually. It happens every year! And also, that’s true only in the center and north. In the southeast and south it gets also way colder in winter. Not snow cold, but like 5°C or a bit less in some extreme occasions.