Which of the following properties does not correspond to the order $HI < HBr < HCl < HF$?

Which of the following oxyacids of chlorine has the highest thermal stability?

Which of the following is the correct increasing order of the reducing power of halide ions?

Observe the following reaction. This reaction represents:
$4 HCl + O_2 \xrightarrow[723 \ K]{CuCl_2} 2 Cl_2 + 2 H_2 O$

The halogen acid used in the preparation of aqua regia is

$MnO_{2} + HCl \xrightarrow{\Delta} A_{(g)}$
$A_{(g)} + F_{2} (\text{excess}) \rightarrow B_{(g)}$
$B_{(l)} + U_{(s)} \rightarrow C_{(g)} + D_{(g)}$
The gases $A$,$B$,$C$ and $D$ are respectively