For the position problem: that's what it is POSITION.
Your main_car/collision_char objects are global, meaning they don't get destroyed between a layout to another.
But it also means that the properties of the objects are kept.
So "On start of layout" you need to "collision_char: Set position to" wherever in the layout you want it.
You also have to store somewhere what part of the layout you want the character to appear to (left or right).
Once again, an invisible object would do the trick, and in "On start of layout", you would pick the according "Spawn_char", left/start or right/end.
Describe the system you exactly want to have all at once, don't go for steps because the previous implementations might become obsolete.