How will you convert ethanol to 2-hydroxy-3-butenoic acid ?

Identify A, B, C and D in the following sequence of reactions:

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\underset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7}{\to }}\mathrm{A}\stackrel{\left[\mathrm{O}\right]}{\to }\mathrm{B} \stackrel{{\mathrm{NH}}_3}{\to }\mathrm{C}\stackrel{\mathrm{Heat}}{\to }\mathrm{D}$

Identify A and B in the following reaction:

$\mathrm{A}\underset{573 \mathrm{K}}{\overset{\mathrm{Cu}}{\to }}\mathrm{B}\underset{{\mathrm{H}}_2\mathrm{O}/\mathrm{Zn}}{\overset{{\mathrm{O}}_3}{\to }}{\mathrm{CH}}_2\mathrm{O}+{\mathrm{CH}}_3{\mathrm{COCH}}_3$

An organic compound A $\left({\mathrm{C}}_4{\mathrm{H}}_{10}\mathrm{O}\right)$ reacts with $\mathrm{HI}$ giving a compound B $\left({\mathrm{C}}_4{\mathrm{H}}_9\mathrm{I}\right)$, which on reduction gives n-butane. On oxidation, 'A' gives a compound C $\left({\mathrm{C}}_4{\mathrm{H}}_8\mathrm{O}\right)$ and then an acid D$\left({\mathrm{C}}_4{\mathrm{H}}_8{\mathrm{O}}_2\right)$.

Deduce the structures of A, B, C and D and mention their IUPAC names.