Which name is incorrect matched for the respective structures:

The true statement about the following corformation is:

The structures $\mathrm{I} \text{and} \mathrm{II}$ are

Incorrect about the compounds $\mathrm{I}, \mathrm{II}, \mathrm{III}$ is:

What is the correct relationship between the following compounds?

${\mathrm{CH}}_3-{\mathrm{CH}}_2-\underset{\stackrel{|}{{\mathrm{CH}}_3}}{\mathrm{CH}}-{\mathrm{CH}}_2-{\mathrm{CH}}_3$,  ${\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_2-\underset{}{{\mathrm{CH}}_2-{\mathrm{CH}}_3}$