The statement that is not true about ozone is:

in the stratosphere, it forms a protective shield against UV radiation.

in the atmosphere, it is depleted by CFCs.

it is a toxic gas and its reaction with NO gives $\displaystyle \mathrm{NO}_2$.

in the stratosphere, CFCs release chlorine free radicals $\displaystyle \left(\mathrm{Cl}^{\cdot}\right)$ which reacts with $\displaystyle \mathrm{O}_3$ to give chlorine dioxide radicals.