Both states and municipalities establish traffic laws. In most instances person exiting a driveway whether private or public will be held accountable for an accident. The premise being, that driver is entering into the "traffic flow" and is required to use reasonable caution and take no action until the right-of-way is safely clear.
The operator of the backing vehicle is always at fault hen a stationary object is struck.
In most states, the driver backing up is always responsible for avoiding a collision unless other circumstances enter into the collision, such as DUI, excessive speed or faulty brakes on the part of the other vehicle. But even then, the responsibility may be "shared".
Was the other vehicle backing as well? If so maybe 50/50. Were you the only one backing and other vehicle traveling down lane? If so 100% on you. Generally, the person backing must use a higher degree of care. Really not enough details to give you a good answer, please supply more and perhaps I can be of more assistance.
Check with the local police but I've had it where people backing a car out of a shop into a private parking lot get hit by someone driving through (too fast even) and the person who is in reverse is always at fault. Might be different in some areas but in my area this is how it goes.
If you were forced into striking another vehicle by a vehicle which struck you first, the vehicle that struck you is (usually) responsible for the entire accident. However, if you are required to have insurance in your state, that will not get you out of any ticket becauise of your lack of insurance.
no unless it has enough force
It is against the law everywhere to block a driveway, and if you were somehow at fault for your trailer being struck, yes. If you were obstructing the driveway with the trailer and it was hit as someone attempted to exit the drive, BOTH you and the other driver could be charged.
Originally you are at fault unless you were in the process of backing up before the offender had arrived. If however he was present before you started to back up and claims he was unable to stop than you were at fault. GOOD LUCK IN COURT :)
The car to the rear, unless the car struck was backing. Depends on the situation.
That would depend on traffic speed, speed of vehicle 2, weather conditions. Purely based on the information given, the vehicle who ran the light would be at fault because they made a maneuver which caused other vehicles to crash.
It would be vehicle 1 because it made vehicle 2 get hit by vehicle three who had nothing to do with it
I don't know the details but most likely the vehicle that struck you is at fault if he/she was traveling in the same direction and lane behind you.