How close do I hold it to the forehead?

Non-contact infrared forehead thermometers are held a short, fixed distance from the forehead, typically a few centimeters. Keep that gap consistent, since readings drift if you move closer or farther away.

Is it accurate enough for a fever?

It gives a fast screening reading, which is what forehead infrared thermometers are designed for. For a confirmed fever, many clinicians suggest following up with a contact thermometer, especially on a very young child.

Can it measure milk, bath water or a room?

Yes. Surface mode reads the temperature of objects and liquids rather than people. Use body mode for forehead readings and surface mode for everything else.

Does it remember past readings?

It stores the previous 32 temperature readings. That lets you scroll back through a fever over a day, but the readings are not tagged by person.

Do I need to convert Celsius to Fahrenheit?

No. You can switch the display between Celsius and Fahrenheit.

Does it come with batteries?

The listing does not say what is included in the box beyond the thermometer. Check the package contents before first use, since handheld thermometers usually need batteries.