$I.\,\,C{H_2} = CH - C{H_3} + \,{H_2}O\,\xrightarrow{{{H^ + }}}$
$II. \,\,C{H_3} - CHO\,\xrightarrow[{(ii)\,{H_2}O}]{{(i)\,C{H_3}MgI}}$
$III. \,\, C{H_2}O\,\xrightarrow[{(ii)\,{H_2}O}]{{(i)\,{C_2}{H_5}MgI}}$
$IV.\,\,C{H_2} = CH - C{H_3}\,\xrightarrow{{KMn{O_4}}}$
$\begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,OH} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,} \\
{C{H_3} - CH = CH - C{H_2} - CH - C{H_3}}
\end{array}$ $\longrightarrow $ $C{H_3} - CH = CH - C{H_2}C{O_2}H$