Which one of the following statements is correct?

When $SO_2$ is passed through a solution of $H_2S$ in water :-

$SO_2$ can be converted into $SO_3$ with the help of:

Which one of the gases dissolves in $H_2SO_4$ to give oleum?

The correct sequence of decreasing number of $\pi$-bonds in the structures of $H_2SO_3$,$H_2SO_4$,and $H_2S_2O_7$ is:

Given below are two statements:
Statement $I$: Oxygen being the first member of group $16$ exhibits only $-2$ oxidation state.
Statement $II$: Down the group $16$ stability of $+4$ oxidation state decreases and $+6$ oxidation state increases.
In the light of the above statements,choose the most appropriate answer from the options given below: