Which one of the following compounds of Group-$14$ elements is not known?

Which of the following is an example of a neutral oxide?

In the following reaction,assign the correct category for the underlined atom in the product of complete hydrolysis at $R.T.$:
$H_3\underset{-}{P}O_5 + H_2O \longrightarrow H_3PO_4 + H_2O_2$

Which of the following compounds is the most volatile among $CH_4, SiH_4, GeH_4, SnH_4$?

Which of the following is true for diamond?

Identify the incorrect statements from the following:
$I.$ Tin in $+2$ state acts as a reducing agent,while lead in $+4$ state acts as a strong oxidising agent.
$II.$ Silicon exists as both $[SiF_6]^{2-}$ and $[SiCl_6]^{2-}$ forms.
$III.$ The hybridisation of carbon in fullerene is $sp^3$.
$IV.$ Among $Ge$,$Sn$,and $Pb$,the lowest melting point is for $Sn$.