You are only allowed to ask one question at a time so I edited out your second question. Since a chlorine radical acts as a catalyst here that means that it must be consumed in the first step and then regenerated in the second step. The chlorine atom reacts with an ozone atom in the first step to produce ClO and O2.
Cl + O3 --> ClO + O2
The second step then involves the ClO reacting with an oxygen radical to regenerate the chlorine radical and produce a second molecule of O2.
ClO + O --> Cl + O2
When the two equations are added together the chlorine radicals cancel each other out and so do the ClO molecules. The net chemical equation is:
O3 + O --> 2O2
This is the equation that you gave in your question.