This depends on which Country you are in? The UK criteria which maybe the same throughout Europe looks for sharp edges and or projections likely to cause personnel injury to pedestrians. The other thing to think about is where the corrosion has formed, is it in such a position that it is likely to injury a pedestrian? If not a pass and advise would be given.
the tailgate unlocks with the rear doors. Are your rear doors unlocking properly ? is your car battery weak ??
remove any rust, buy a good quality rust prevention products eastwood.com has some good ones, apply a liberal amount where water can seep in and cause rust.
From the outside.
the rear speakers are located in the back doors. you have to remove the door panels to get at them.
The muffler may have a hole in it due to rust.
maybe it is because the outside locks are broken
6x9 in rear, 6 inches in front doors.
Surface rust isn't dangerous, cancerous rust on the frame can be dangerous because the car could snap in half depending on the extent of the rust. The best solution usually is just to get a new car because the frame usually isn't worth fixing. In my state they consider it dangerous because if you get stuck in snow they fear exhaust entering the cabin and killing its occupants. Rust holes of any kind will fail your inspection.
Car magnets doesn't cause rust.
You are. Improper backing.
Rust is formed when iron reacts with oxygen in the air. It's not erosion, it's a chemical change called oxidation.
The Ford Crown Victoria police interceptor car would catch fire after a high-speed rear collision. Also the steel wheels would rust and the rack and pinion steering units would fail prematurely. The weld points in the wheels would come loose.