Which of the following dinegative anions is quite common?

For the preparation of sodium thiosulphate by the "Springs reaction",the reactants used are

Consider the following statements in respect of oxides of sulphur.
$(1)$ In gas phase $SO_2$ molecule is $V$-shaped.
$(2)$ In gas phase $SO_3$ molecule is planar.
$(3)$ $\gamma-SO_3$ is a cyclic trimer.
Which of the above statements are correct?

Among the elements of group $16$,which element exists in a metallic lattice in its monoatomic state and also exhibits two crystalline forms,$\alpha$ and $\beta$?

Ozone,when reacts with potassium iodide solution,liberates a certain product which turns starch paper blue. The liberated substance is......

Justify the placement of $O$,$S$,$Se$,$Te$,and $Po$ in the same group of the periodic table in terms of electronic configuration,oxidation state,and hydride formation.