1st one is the back-up light switch. It turns on the white light at the back when you put the gear in reverse.
2nd one is the signal wire to the ignition coil so that it can fire the plug. If there are two wires coming out, the other may be for cng kit to tell that the engine is running.
3rd is the coolant temperature gauge. It senses the temperature here and shows the reading in the cluster. Its a single wire component.
4th is the radiator fan switch. it turns on the radiator fan when the operating temperature of the engine is reached. Yours is not connected which means your radiator fan is direct. Please make it functional and have mercy on your car. If you could connect wires to it well and good other wise replace it with a working one. To check its operation, consult the service manual.
The temperature sensor is below the thermostat valve so that it can sense the temperature of the coolant in the engine block whether the valve is open or not. The fan switch is above the valve so that when the valve opens, the switch toggles due to hot coolant and thus turns on the fan.