The increasing order of the reactivity of the following halides for the S_N1 reaction is :

Which of the following, upon treatment with tert-BuONa followed by addition of bromine water, fails to decolorize the colour of bromine?

3-Methyl-pent-2-ene on reaction with HBr in presence of peroxide forms an addition product. The number of possible stereoisomers for the product is :

The major product obtained in the following reaction is :