The bond line formula of $HO-CH(CN)_2$ is:

The $IUPAC$ name of the following compound is

As per $IUPAC$ rules,which one of the following groups will be regarded as the principal functional group?

Which of the following $IUPAC$ names is correct for the structure:
$CH_3-CH(CH_3)-CH_2-CH_2-CH_2-CH(CH_2-CH_2-CH_3)-CH_2-CH_3$?
$(i)$ $2-$methyl$-6-$ethylnonane
$(ii)$ $6-$ethyl$-2-$methylnonane
$(iii)$ $4-$ethyl$-8-$methylnonane

The $IUPAC$ name of $CH_2 = CH - CH(CH_2CH_3) - C(Br) = CH_2$ is ...

What is the $IUPAC$ name for the given compound?