Which of the following reactions end in finite time?

For a zero order reaction $A \longrightarrow \text{product}$,consider the following graph:
Where $[A_t]$ is the remaining concentration of reactant $A$ at time $t$. Calculate the concentration of $A$ after $2 \ s$. (in $mol/L$)

Which of the following graphs most appropriately represents a zero order reaction?

For a zero order reaction $A \longrightarrow \text{product}$,the concentration of $A$ decreases from $0.8 \ mol \ dm^{-3}$ to $0.2 \ mol \ dm^{-3}$ in $6 \ minute$. What is the rate constant of the reaction?

In the reaction,$A \rightarrow$ products,if the concentration of the reactant is doubled,the rate of the reaction remains unchanged. The order of the reaction with respect to $A$ is

For a certain reaction,$10\%$ of the reactant dissociates in $1 \ hour$,$20\%$ of the reactant dissociates in $2 \ hour$,and $30\%$ of the reactant dissociates in $3 \ hour$. What are the units of the rate constant?