Which of the following cannot be reduced by hydrogen?

Among the following,the correct statements are:
$I$. $LiH, BeH_2$ and $MgH_2$ are saline hydrides with significant covalent character.
$II$. Saline hydrides are volatile.
$III$. Electron-precise hydrides are Lewis bases.
$IV$. The formula for chromium hydride is $CrH$.
The correct option is:

Match List-$I$ with List-$II$.

List-$I$ (Hydrides)	List-$II$ (Nature)
$a. MgH_2$	$i. \text{Electron precise}$
$b. GeH_4$	$ii. \text{Electron deficient}$
$c. B_2H_6$	$iii. \text{Electron rich}$
$d. HF$	$iv. \text{Ionic}$

Choose the correct answer from the options given below:

How many isotopes of Hydrogen are there? Give their names.

Which element accepts one electron to achieve a noble gas-like configuration?

Which of the following reactions can produce hydrogen gas?