Among the fluorides below,the one which does not exist is

Which of the following statements is $NOT$ true for noble gases?

Which of the following chemical reactions of xenon is $NOT$ correct?

Which of the following methods is used for the separation of noble gases?

$Xe + 2F_2 \xrightarrow[673 \ K, 5-6 \ bar]{Ni} ?$
Which compound is formed by the above reaction?

Which statements among the following are correct about Helium?
$(i)$ Liquid helium is used to sustain powerful superconducting magnets.
$(ii)$ Liquid helium is useful to carry low temperature experiments.
$(iii)$ It is a heavy gas.
$(iv)$ It is a flammable gas.