What is the oxidation number of $S$ in $SO_3^{2-}$?

In which of the following compounds is chlorine in the $+1$ oxidation state?

The order of the oxidation state of the phosphorus atom in $H_3PO_2$,$H_3PO_4$,$H_3PO_3$,and $H_4P_2O_6$ is:

The oxidation number of sulphur in $H_2SO_4$ is

The oxidation number of $As$ in $H_2AsO_4^-$ is:

$A$ compound contains $x$,$y$,and $z$ atoms. The oxidation number of $x$ is $+3$,$y$ is $-5$,and $z$ is $+1$. The possible formula of the compound is: