(a) (i)
$+{\mathrm{NH}}_2\mathrm{OH}+{\mathrm{H}}^{+}\to {\mathrm{CH}}_3\mathrm{CH}=\mathrm{N}-\mathrm{OH}$ $+{\mathrm{H}}_2\mathrm{O}$
A-Acetaldehyde
B-Acetaloxide
(ii) The IUPAC name is 3-bromobenzaldehyde.
(iii) Phenol and Benzoic Acid can be distinguished by iron chloride $\left({\mathrm{FeCl}}_3\right)$ test. As phenol gives violet colouration with neutral ${\mathrm{FeCl}}_3$ solution while benzoic acid gives buff coloured precipitate of ferric benzoate.
$6{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}+{\mathrm{FeCl}}_3\to {\left[\mathrm{Fe}{\left({\mathrm{OC}}_6{\mathrm{H}}_5\right)}_6\right]}^{3-}+3{\mathrm{H}}^{+}$

$3{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}+{\mathrm{FeCl}}_3\to {\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COO}\right)}_3\mathrm{Fe}+3\mathrm{HCl}$ Violet complex $+3\mathrm{HCl}$
$\underset{\mathrm{Benzoic}\mathrm{acid}}{3{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}}+{\mathrm{FeCl}}_3\to \underset{\mathrm{Buff}\mathrm{coloured}\mathrm{ppt}.}{{\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COO}\right)}_3\mathrm{Fe}}$ $+3\mathrm{HCl}$
OR
(b) (i) Benzoic acid to benzaldehyde - Firstly benzoic acid is converted into benzoyl chloride by adding sulphonyl chloride and then by Rosenmund reduction reaction using $\mathrm{Pd}-{\mathrm{BaSO}}_4$ converted into benzaldehyde.

(ii) Propan-1-ol to 2-bromo propanoic acid -Firstly propanol is converted into propanoic acid by oxidizing in presence of alk. ${\mathrm{KMnO}}_4$ and then by using Red Phosphorous/ $\mathrm{NaOH}$ and Bromine gas is further converted into 2-Bromo-propanoic acid

$\underset{2-\mathrm{Bromopropanoic}\mathrm{acid}}{{\mathrm{CH}}_3-\underset{\mathrm{Br}}{\underset{|}{\mathrm{CH}}}-\mathrm{COOH}}$
(iii) Ethanal or Acetaldehyde into But-2-en-1-al Aldol condensation (in presence of dil $\mathrm{NaOH}$ ) followed by dehydration.
$\underset{-{\mathrm{H}}_2\mathrm{O}}{\overset{\mathrm{\Delta }}{\mathit{─}\mathit{─}\mathit{─}\mathit{─}▸}}\underset{\mathrm{But}-2-\mathrm{en}-1-\mathrm{al}}{{\mathrm{CH}}_3-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}}$