Which of the following aldehydes has a buttery odour?

Provide the $IUPAC$ name and structure for the following compounds:
$(i)$ Propanone
$(ii)$ Butanone
$(iii)$ Hexan$-3-$one
$(iv)$ $2,4-$dimethylpentan$-3-$one
$(v)$ Pentan$-3-$one
$(vi)$ $2-$methylcyclohexanone
$(vii)$ $4-$methylpent$-3-$en$-2-$one
$(viii)$ Benzophenone
$(ix)$ Acetophenone
$(x)$ $3-$methylbutan$-2-$one
$(xi)$ $5-$hydroxy$-5-$methylhexan$-3-$one
$(xii)$ $3-$oxobutanoic acid
$(xiii)$ $3,3-$dimethylheptan$-2,6-$dione.

The molecule having a formyl group is

Identify the functional group present in Vanillin.

Chloral is

Which of the following is the correct $IUPAC$ name for the given structure?