Which of the following orders of rotation barrier about the $C=C$ bond,as indicated in the structures $(I)$,$(II)$,and $(III)$,is correct?

Which of the following statements are not correct?
$a$. The energy of resonance hybrid structure is higher than that of the possible canonical structures of the molecule.
$b$. When inductive effect and electromeric effect operate in opposite directions,electromeric effect predominates.
$c$. When the $\pi$ electrons of the multiple bond are transferred to that atom to which the attacking reagent does not get attached,it is known as $+E$ effect.
$d$. The resonance structures with separation of opposite charges are more stable.

Represent the three types of electron movement in organic reactions.

Identify the species from the following that exhibits no-bond resonance.

The rate of attack of an electrophile is least when $X$ in the given compound is

Find the number of hyperconjugation structures in the isopropyl carbocation.