The incorrect statement is:

• Correct answer
  A

  $\mathrm{L}\mathrm{i}\mathrm{N}{\mathrm{O}}_3$ decomposes on heating to give $\mathrm{L}\mathrm{i}\mathrm{N}{\mathrm{O}}_2$ and ${\mathrm{O}}_2.$
• B

  $\mathrm{L}\mathrm{i}\mathrm{C}\mathrm{l}$ crystallises from aqueous solution as $\mathrm{L}\mathrm{i}\mathrm{C}\mathrm{l}-2{\mathrm{H}}_2\mathrm{O}$ .
• C

  Lithium is the strongest reducing agent among the alkali metals.
• D

  Lithium is least reactive with water among the alkali metals.

Hence, the correct answer is option: 'A'.