What is the common name of the compound $CH_2=CH-CHO$?

Identify the ketone from the following.

Formalin is an aqueous solution of which of the following?

Explain the bond formation and structure of the carbonyl group with a suitable diagram.

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 $IUPAC$ name of the given compound is: