What are the uses of alkyl halides?

Which of the following statements is true in case of alkyl halides?

On treating a mixture of two alkyl halides with sodium metal in dry ether, 2-methylpropane was obtained. The alkyl halides are

What is the reagent used in the conversion of alkyl halide into alkene?

In Wurtz synthesis, the reactivity of alkyl halides with sodium metal follows the order :