Which one of the following compounds does not form an ozonide?

Which of the following has the highest octane number?

The number of secondary hydrogens in $2, 2-$dimethylbutane is

The correct order of boiling points of the following molecules is:
$(i)$ $n$-Hexane
$(ii)$ $2$-methylpentane
$(iii)$ $2,3$-dimethylbutane

The octane number $100$ is assigned to .............

$(i)$ Give the reaction for the bromination of ethane.
$(ii)$ Is this reaction suitable for obtaining pure bromoethane? Why?
$(iii)$ Give the name of the reaction mechanism and the names of the stages occurring in the reaction.
$(iv)$ Give the reaction for the first stage.
$(v)$ Which type of bond cleavage occurs in the first stage?