At what Temperature does the thermostat open. And what is a normal operating temperature?

The thermostat will open as soon as the engine starts to warm (180-200) and normal operating temperature is around 180-200 (the arm should reach about center on the gauge)

*OBDII* most are normally upwards of 200 degreesF , the coolant fans normally cycle on at just above 215 on most. OEM thermostat 195 on many-- Mistakenly many people put lower temp. t-stats in to help with overheating issues , usually making things worse. The cooler the engine runs , the less efficient it is.