Statement–I: Order of a reaction cannot be negative.
Statement–II:  Time taken for completion of a first order reaction is double its half life period.
 

(I) Consider a reaction in which rate becomes half when concentration of reactant is doubled. 
Then          $$\begin{gathered} {\mathrm{C}}^{\mathrm{n}}\mathrm{\alpha }\mathrm{rate} \\ {2}^{\mathrm{x}}=\frac{1}{2} \\ \mathrm{x} =–1 \end{gathered}$$

order of the reaction is –1

$\therefore$       order can be negative.

(II) Time taken for a first order reaction is infinity.
First order reaction never goes to completion.