Find out the incorrect relation in the following pair of compounds:

Given below are two statements :
Statement $(I) :$ $CH_3CH=CHCH_3$ and $cyclobutane$ are isomeric compounds.
Statement $(II) :$ $CH_3CH_2CH_2CH_2NH_2$ and $(CH_3CH_2)_2NH$ are functional group isomers.
In the light of the above statements,choose the correct answer from the options given below :

Identify the type of isomerism shown by the following structures:

Identify the correct statement among the following:

In which structure is the central carbon $(C-3)$ not a chiral centre?

The two compounds $CH_3CH_2CH_2OCH_3$ and $CH_3CH_2OCH_2CH_3$ are examples of which type of isomerism?