when the watch worn on the arm, which by the human body haetm the tempearature value Display on the screen will be higher than room temperature. So if you want to get the room temperature, please put the watch on a table, and avoid direct sunlight on it, the actual room temperature will be on the watch after 20 minutes

Can be used for 8-12 months. There are a big battery is CR2025 is the electronic screen battery, the small battery is SR626SW is the pointer battery, you can put a coin turn contrarotate backside.

Can't, Considering diving safety, button are closed under diving mode, expect "light" buttom.

Screen protector glss dia is 40mm.