Inoperable means unable to be fixed via surgery.
Drop a line!
A timing chain or belt is worn so sloppy that it jumps a tooth on the sprockets creating loss of power and performance, jumping more than a tooth would render the engine inoperable and in some cases destroy the engine in an interference engine.
The cooling fan may be inoperable, either the fan clutch is bad or the electric cooling fan isn't working. Need to know what year, make and model vehicle you have to help you more.
Thermostat, low coolant, inoperable fan, exhaust leak close to engine bay
Low coolant, missing belt, failed water pump, inoperable fan, warped/cracked head, restricted radiator, etc.
Yes, along with dozens of other things.
it is basically impossible. the engine computer reads a code from your key and then determines if the proper key is in the ignition. without receiving this code, the engine computer is permanently inoperable.
You die!
Fourth stage is usually terminal and inoperable. Radiation may slow the process.
thay cant do anything
Your valves will bend and the vehicle will be inoperable/undriveable. If the engine is a non-interferance engine, the valves won't get bent. You could remove the timing belt cover and see with your eyes if the belt is broken. A compression test will also give you a clue, the compression will be 0 in all cylinders.