What is the type of delocalization involving $\sigma$ bond orbitals called?

Which one of the following represents the hyperconjugation effect?

The correct stability order of the following species is:

Identify the lowest positive charge developed (indicated by $\delta, \delta_1, \delta_2, \delta_3$) due to the inductive effect in the following compound: $CH_3-CH_2-CH_2-CH_2-Cl$.

In which of the following groups is the $(-M)$ effect observed?

Which of the following is not correct?