When I duplicate my scene- level 1 to make level 2, the prefabs I change in level 2 change the prefabs in level 1 and vice versa.
This happens because you are using the same prefab in both levels 1 and 2. My solution for this would be to create a directory for both Levels and make separate prefabs and scripts for both of them. Level 1’s prefabs go in the Level 1 directory, and the same thing with Level 2. You can name your prefabs and scripts with the level number at the end.
Assets > Level01 > CamControllerL1, CarPrefabL1
Assets > Level 02 > CamControllerL2, CarPrefabL2
I really hope this helps you