Which form of $UV-$radiation is allowed to pass through ozone and reach the earth surface?

The Montreal Protocol is aimed at:

What is the result of the action of ultraviolet $(UV)$ rays on molecular oxygen $(O_2)$?

What is the significant date associated with the Montreal Protocol?

The stratospheric ozone depletion leads to:

Which of the following statement$(s)$ is/are correct?
$(i)$ The Montreal Protocol was signed in $1987$ and became effective in $1989$.
$(ii)$ 'Good' ozone is found in the troposphere.
$(iii)$ Ozone is formed by the action of $UV$ rays on molecular oxygen and degrades into molecular oxygen.
$(iv)$ $CFCs$ are responsible for the imbalance between the production and degradation of ozone.
$(v)$ $DNA$ and proteins of living organisms absorb $UV$ rays.