The year, make, model and engine info would help.
It will Start and Run!
If the key is in the on position and the engine is not running, the fuel pump is off. If the engine is running then the fuel pump is also. During the start cycle the pump will only run for 3 seconds unless the engine starts.
ignition swithc could be broken, I suggest you have it looked at to be sure
Yes it can
It is based on the Otto Cycle operation ...
When a position sensor is going bad the engine could run rough, or cut off for no apparent reason. Or, the engine may not start at all.
It will for maybe 3 seconds , when the key is turned to the run position , before you start the Explorer
Hold the trip meter button in while turning the ignition to run position. Do not start the engine. Turn off key and then start the engine.
It may not ruin the engine, but it will foul the spark plug, making the engine run rich and/or hard to start. Will also emit a lot of gray smoke.
Only if the engine was designed to run on diesel.
Some vehicles have the Accessory position in the opposite direction from the Run/Start position.
With a 2 stroke or 2 cycle engine if the ignition timing is set too close to top dead center it can start to run backwards.