Buying a film
compact camera.

Essentially the lens and the automation. A 40-euro compact has a three-element lens, fixed focus and two or three exposure steps: it always shoots the same. A high-end 1990s model has a six-element lens, autofocus and real metering, which is why it costs ten times as much.

Yes, as long as you understand what it does. It focuses acceptably from about a metre and a half to infinity and no further. For street and holiday photography in good light it works very well; for close portraits or dim interiors it does not.

It depends. The mechanical bodies of the 1960s and 1970s fire without a battery; the flash, if there is one, does need power. Compacts from the 1980s and 1990s do not work without a battery, and there you must check the compartment has not leaked, because the corrosion eats the contacts and often cannot be fixed.

Because of how the images look: high contrast, saturated colour and vignetting, which is exactly what phone filters imitate. That has pushed the price of a few specific models far above what they are technically worth.

A simple, cheap mechanical one, to learn how to load a roll and how film behaves without risking much money. Once you know whether you enjoy the process, you can move up to better glass.