No, an ozone layer is not a requirement but it wouldn't hurt anyway if one wants to terraform Mars. Mars would need a strong magnetosphere instead and/or a higher mass/gravity to hold a 1 atm like atmosphere.
Well, first of all it is critical to understand that angular momentum is conserved. This is a very fundamental law of physics and, by Noether's theorem, is a consequence of (or is equivalent to) the rotational invariance of space: the laws of physics are unchanged by rotations.
What this means is that the only way you can do something like this is to ...
Put simple nuclear rockets on Venus, attached to Venus on Rocky mountains. Keep them running for many years. This might speed rotation of planet. Or use 🚀 rockets attached to Venus to turn entire planet into giant spaceship, to put planet in habitable zone orbit.🙂. Terraform Venus and live there. Do similar to other planets.