Which of the following elements is $NOT$ radioactive?

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

The incorrect statement regarding the following reactions is:
$XeF_6 + \text{Excess } H_2O \rightarrow 'X' + HF$
$XeF_6 + 2 H_2O \rightarrow 'Y' + HF$

Which of the following is an inert element?

Which one of the following does not exist?
$(i)$ $XeOF_{4}$
$(ii)$ $NeF_{2}$
$(iii)$ $XeF_{2}$
$(iv)$ $XeF_{6}$

Which element among the following does $NOT$ form diatomic molecules?