What is temperature at which liquid turns to gas?

It's different for every gas. It also depends on the pressure. You actually need a two-dimensional depiction called a phase diagram. Check out the Wikipedia article on 'vapor'. You also need to consider that most substances will have a non-zero vapor pressure at temperatures below their boiling points and at least down to their freezing points. As long as you're not interested in some pedantic definition of gas which differentiates it from vapor, there is no specific temperature at which a gas turns to liquid, or vice versa.

answ2. A gas turns into a liquid at its condensation temperature, or in the reverse direction, a liquid turns into a gas at its boiling point.