Yes.
bad gas mileage, hard starting, and basically bad performance.
Spark Plugs do not affect your alternator. As long as your engine is running then it should be charging unless your alternator is bad
No spark from coil, bad plug wires, or bad plugs.
No, but burning oil will give you bad spark plugs.
having bad spark plugs could effect how the spark sparks and when it sparks. new plugs is never a bad idea
Yes, a bad coil will affect any combination or all of the cylinders - it is the source of all spark required for firing the spark plugs and making the engine run.
you are not getting spark. this could be from a bad alternator, bad spark plugs, bad spark plug wires, or bad engine coils. The spark plugs and wires are the cheapest so try putting in new ones of those first.
It should make it run better and get better mileage after you replace the plugs with new ones. You may also want to replace the plug wires if the car has over 100,000 miles or is 10 years old.
Bad spark plugs, spark plugs wires, etc.
it is probably caused by bad spark plugs, spark plug wires and you need anew air filter
No.
Spark plugs don't smoke. A bad alternator would cause a dead battery.