What is the correct order of solubility of $He, Ne, Ar, Kr,$ and $Xe$ in water?

Which of the following does not exist?

What is the atomic state of noble gases?

$Xe_{(g)}$ and $F_{2(g)}$ react in the ratio $1:20$ at $573 \ K$ and $60-70 \ bar$ to form $A$. When $A$ is completely hydrolyzed,$B$ and $HF$ are formed. $A$ and $B$ are respectively:

$XeF_6$ on partial hydrolysis with water produces a compound '$X$'. The same compound '$X$' is formed when $XeF_6$ reacts with silica. The compound '$X$' is

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.