As a general rule, a parked or stopped vehicle is almost never At Fault for an accident. The onus is on the driver of the moving vehicle to make sure the way is clear.
The person who hit a parked vehicle is at fault.
Yes, private property does not obsolve you of your responsiblity.
You do.
In the UK it can, if the driveway is private property.
yes
you are
private property impound - possibly due to parked in a private lot
The person who caused the damage.
The driver that hit the parked vehicle would be at fault.
nothing
If a car is parked next to my fence is that OK?
A parked car almost never crashes into others or does anything else that prevents other drivers on private property from stopping in time to avoid hitting it. Therefore, the fact that it may be "illegally parked" usually has nothing to do with why someone negligently crashed into it.