Which of the statements given below is incorrect?

Which of the following sets of atomic numbers corresponds to elements of group $16$?

Sulphur trioxide can be obtained by which of the following reactions?

Peroxodisulphuric acid $(H_2S_2O_8)$ contains which of the following bonds?

Which of the following molecules exhibits the lowest thermal stability?

An amorphous solid $'A'$ burns in air to form a gas $'B'$ which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous $KMnO_4$ solution and reduces $Fe^{3+}$ to $Fe^{2+}$. Identify the solid $'A'$ and the gas $'B'$ and write the reactions involved.