In other words, what is the Condensation Point of water?
The dew point is the point at which liquid water would condense from the atmosphere, and the frost point is the temperature at which ice would form from the atmosphere. Both are functions of temperature, pressure, and the water content of the atmosphere.
At what temperature, can you say for certain that all water vapor will turn into liquid?
At absolute zero there would be no gaseous water.
For temperature above 0 Kelvin and 273.15 Kelvin (0 Celsius) or below then water condensing from the atmosphere would form ice.
For temperature between 0 Celsius and 100 Celsius liquid water would condense.
Above 100 Celsius water wouldn't condense unless the gas phase of the system was under pressure.