Formic acid and acetic acid differ in which of the following?

In the esterification of a carboxylic acid,the other reagent used is:

Consider the acidity of the following carboxylic acids:
$(I)$ $PhCOOH$
$(II)$ $o-NO_2C_6H_4COOH$
$(III)$ $p-NO_2C_6H_4COOH$
$(IV)$ $m-NO_2C_6H_4COOH$
Which of the following is the correct order of acidity?

$EtO-CO-OEt \xrightarrow[(2) H_3O^{+}]{(1) CH_3MgBr \text{ (excess)}} (A)$,Product $(A)$ is:

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:

Between $CH_3COOH$ and $HCOOH$,$HCOOH$ will be: