Oxalic acid may be distinguished from tartaric acid by

Predict $A$ and $B$ in the following reaction sequence:

Among the following acids,which has the lowest $pK_a$ value?

Identify the product $Z$ in the following reaction sequence:
$Cyclohexene$ $\xrightarrow{KMnO_4} X$ $\xrightarrow{Ca(OH)_2} Y$ $\xrightarrow{\Delta} Z$

Arrange the following compounds in decreasing order of reactivity for the hydrolysis reaction:
$(I) C_6H_5COCl$
$(II) NO_2-C_6H_4-COCl$
$(III) CH_3-C_6H_4-COCl$
$(IV) OHC-C_6H_4-COCl$

The descending order of acidity for the following carboxylic acids is:
$A.$ $CH_3COOH$
$B.$ $F_3C-COOH$
$C.$ $ClCH_2-COOH$
$D.$ $FCH_2-COOH$
$E.$ $BrCH_2-COOH$
Choose the correct answer from the options given below: