Which of the following is used to prepare $Cl_2$ gas at room temperature from concentrated $HCl$?

Write balanced chemical equations for the following:
$(i)$ $NaCl$ is heated with concentrated sulphuric acid $(H_{2}SO_{4})$ in the presence of manganese dioxide $(MnO_{2})$.
$(ii)$ Chlorine gas $(Cl_{2})$ is passed into an aqueous solution of sodium iodide $(NaI)$.

The colour of the $X_2$ molecules of group $17$ elements changes gradually from yellow to violet down the group. This is due to
[$A$] the physical state of $X_2$ at room temperature changes from gas to solid down the group
[$B$] decrease in $HOMO-LUMO$ gap down the group
[$C$] decrease in $\pi^*-\sigma^*$ gap down the group
[$D$] decrease in ionization energy down the group

Which of the following substances act as a fluorinating agent?

Which of the following halogens does always show an oxidation state of $-1$?

Which of the following is used in the preparation of chlorine?