Temperature gauge

I have had my RS200 cup a little over a month now and my coolant temperature gauge seems to cool down if I'm going more than 30mph. Some forums on here talk about that being a broken thermostat? Is that definitely what it is and would that cause any damage to the car? Also, does the car have an oil thermostat even if it doesn't display it? I'd like to buy a bluetooth OBD port device to notify my phone when the oil is up to temperature so I don't damage the engine by going above 3k rpms when cold.
 
The temperature gauge should sit between the second and third markers. It always looks as if the car is cool even when it is up to temperature,

The Clio does not measure oil temperature in a way that you can read it from a dongle. If you want to know what temperature the oil is you will need to install a sensor.