Which is the lightest gas?

Which of the following statements is not correct?

Give the reaction of methane with steam for the production of dihydrogen.

The name hydrogen was given by

Consider the following statements:
$1.$ Atomic hydrogen is obtained by passing hydrogen through an electric arc.
$2.$ Hydrogen gas will not reduce heated aluminium oxide.
$3.$ Finely divided palladium adsorbs large volume of hydrogen gas.
$4.$ Pure nascent hydrogen is best obtained by reacting $Na$ with $C_2H_5OH$.
Which of the above statements is/are correct?

The correct order of boiling point of $H_2$,$HD$,$D_2$ and $T_2$ would be