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

Which of the following is the only existing oxoacid of fluorine?

Which one of the following statements is not correct?

Phosphorus reacts with $SO_2Cl_2$ to form $PCl_5$ and $X$. At $723 \ K$,$HCl$ gas reacts with $O_2$ in the presence of $CuCl_2$ to form water and $Y$. $Y$ reacts with $X$ in water to form two acids $A$ and $B$. What are $A$ and $B$ respectively?

The correct order of bond dissociation enthalpy of halogens is:

Give reason to explain why $ClF_3$ exists but $FCl_3$ does not exist.