Time required for $100\%$ completion of a zero order reaction is

Which among the following reactions is an example of a zero-order reaction?

Which of the following statements about zero order reaction is not true?

Which of the following is correct for a zero-order reaction?

Consider the reaction $aX \to bY$, for which the rate constant at $30^\circ C$ is $1 \times 10^{-3} \text{ mol L}^{-1} \text{ s}^{-1}$. Which of the following statements are true?
$A$. When concentration of $X$ is increased to four times, the rate of reaction becomes $16$ times.
$B$. The reaction is a second order reaction.
$C$. The half-life period is independent of the concentration of $X$.
$D$. Decomposition of $N_2O_5$ is an example of the above reaction.
$E$. $\ln \frac{[R]_0}{[R]}$ vs time is valid for the above reaction.

What is the formula to find the value of $t_{1/2}$ for a Zero Order Reaction?