How do ortho and para hydrogen differ from each other?

Under what conditions can hydrogen behave as a metal?

Which one of the following is the most abundant element in the universe?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: Loss of electron from hydrogen atom results in a nucleus of $\sim 1.5 \times 10^{-3} \ pm$ size.
Reason $(R)$: Proton $(H^+)$ always exists in combined form.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following reactions give $H_2$ as one of the products? (Reactions are not balanced)
$I) NaBH_4 + I_2 \longrightarrow$
$II) B_2H_6 + N(CH_3)_3 \longrightarrow$
$III) Al + NaOH + H_2O \longrightarrow$
$IV) BF_3 + NaH \longrightarrow$

The synonym for water gas when used in the production of methanol is: