Which of the following is not a chalcogen?

Which of the following ions does not have $S-S$ linkage?

In the following reaction,assign the product of complete hydrolysis at $R.T.$ for the underlined atom:
$\underline{S}OF_4 + H_2O \longrightarrow H_2SO_4 + HF$

Which of the following ions possesses an $S-O-S$ bond?

Assertion : Both rhombic and monoclinic sulphur exist as $S_8$ but oxygen exists as $O_2$.
Reason : Oxygen forms $p\pi-p\pi$ multiple bond due to small size and small bond length but $p\pi-p\pi$ bonding is not possible in sulphur.

Name the gas that can readily decolourise acidified $KMnO_4$ solution.