Which of the following elements among $He, Ar, Kr,$ and $Xe$ forms compounds in the least amount?

Determine the name and symbol of the element with atomic number $118$.

The number of peroxide bonds in the perxenate ion $[XeO_6]^{4-}$ is ........

The number of $p \pi-d \pi$ 'pi' bonds present in $XeO_3$ and $XeO_4$ molecules,respectively,are

$Xe_{(g)} + 3F_{2(g)} \xrightarrow{573 \ K, 60-70 \ bar} XeF_{6(s)}$ ($1:20$ molar ratio).
$XeF_6 + H_2O \rightarrow XeOF_4 + 2HF$ $(Y)$
$XeF_6 + 3H_2O \rightarrow XeO_3 + 6HF$ $(Z)$
The correct statements regarding $Y$ and $Z$ are:
$I$. $Y$ has square pyramidal geometry
$II$. $Y$ has linear geometry
$III$. $Z$ has $3 \sigma, 3 \pi$ bonds and $1$ lone pair of electrons on the central atom
$IV$. $Z$ has tetrahedral geometry

Who among the following first prepared a stable compound of a noble gas?