What is the decreasing order of reactivity of $HX$ in the reaction $ROH + HX \to RX + H_2O$?

$CH_3 CH_2 OH \underset{\text{step-}1}{\stackrel{Cl_2}{\longrightarrow}} CH_3 CHO$ $\underset{\text{step-}2}{\stackrel{3 Cl_2}{\longrightarrow}} Cl_3 CCHO$
In the above reactions,the role of $Cl_2$ in step-$1$ and step-$2$ respectively is:

The compound which gives turbidity immediately with Lucas reagent at room temperature is

Which of the following reagents would distinguish $cis$-cyclopenta-$1,2$-diol from the $trans$-isomer?

The compound $A$ when treated with ceric ammonium nitrate solution gives a yellow precipitate. The compound $A$ is

Absolute alcohol is: