Liquid level sensor SN-LLS

hi, i'm using this sensor in my project. i have a few questions to ask.
1. is it sure that the middle port of the sensor is not needed?
2. can the entire sensor immersed in the water tank? is it water proof?
3. how many millilitre of water can it measure? ( the sensor length is around 25cm. what if my tank is more than 30cm? )
4. how the sensor can be controlled by the microcontroller? is it required any kit? can it operation with only assembly language or C language better?
1. is it sure that the middle port of the sensor is not needed?
2. can the entire sensor immersed in the water tank? is it water proof?
3. how many millilitre of water can it measure? ( the sensor length is around 25cm. what if my tank is more than 30cm? )
4. how the sensor can be controlled by the microcontroller? is it required any kit? can it operation with only assembly language or C language better?