Who gave the term $isomerism$?

The following compounds are identical with respect to:

The number of stereoisomers obtained by bromination of $trans-2-butene$ is

Total number of stereo-isomers possible for the following compound is:
$1,2$-disubstituted cyclohexane with a $-\text{CH}_2\text{OH}$ group at position $1$ and a $-\text{CH}=\text{CH}-\text{CH}=\text{CH}-\text{CH}_2\text{CH}_3$ group at position $2$.

Consider the following structures. Which statement is $NOT$ correct?

Which of the following options is the correct order of relative stabilities of cations $I$,$II$,and $III$ as shown below (most stable first)?
$(I) \, C_6H_5CH_2^+$
$(II) \, CH_2=CH-CH_2-CH^+-CH_3$
$(III) \, (CH_3)_3C^+$