$IUPAC$ name of the following compound $NC-CH_2-CH(CN)-CH_2-CN$ is:

Name the following compounds according to the $IUPAC$ system:
$(i)$ $CH_3-CH(CH_2Cl)-CH(CH_2OH)-CH(CH_3)-CH_3$
$(ii)$ $CH_3-CH(CH_3)-CH_2-CH(OH)-CH(CH_2OH)-CH_3$
$(iii)$ $3-$Bromocyclohexanol (structure implied)
$(iv)$ $H_2C=CH-CH(OH)-CH_2-CH_2-CH_3$
$(v)$ $CH_3-C(CH_3)=C(Br)-CH_2OH$

What is the $IUPAC$ name of the compound: $CH_3-CH_2-CH(CH_3)-CH_2-COCl$?

Fill in the blanks:
$(1)$ ....... model indicates only bonds in a molecule.
$(2)$ Only ......... model of a molecule indicates both bonds as well as atoms.
$(3)$ In the nomenclature of cyclic compounds,the ....... prefix is written before the name of the simple chain containing alkane.
$(4)$ The names of $C_{20}H_{42}$ and $C_{30}H_{62}$ are ........... and .......... respectively.

The $IUPAC$ name of the following compound is:

Which functional group from the following is considered as the principal functional group if a polyfunctional compound is to be named by the $IUPAC$ system?