The reaction of $K_2Cr_2O_7$ with $NaCl$ and conc. $H_2SO_4$ gives

Which one of the following statements is not correct?

An inorganic white crystalline compound $(A)$ has a rock salt structure. $(A)$ on reaction with conc. $H_2SO_4$ and $MnO_2$ evolves a pungent smelling,greenish-yellow gas $(B)$. Compound $(A)$ gives a white precipitate of $(C)$ with $AgNO_3$ solution. Compounds $(A)$,$(B)$,and $(C)$ will be respectively:

Consider the following reactions:
$(A) (\text{Ionic halide}) + (B) (\text{Good oxidising agent}) + \text{conc. } H_2SO_4 \to (C) (\text{Red-Orange gas is evolved with few by-products})$
$(D) (\text{Other ionic halide}) + (B) + \text{conc. } H_2SO_4 \to (E) (\text{Has same colour as } (C))$
Which of the following properties are different for $(C)$ and $(E)$?

The property/properties that show irregularity in the first four elements of group-$17$ is/are:

The correct order of acidic strength is: