Q: car won't start

car was working parked it the next morning would not start it turns over but will not fire changed a bunch of stuff on it checked the fuel filter checked the fuel pump changed the fuel regulator smelled like possibly had water in fuel so I added seafoam and heat to the tank done all kinds of stuff to it I check the spark replaced sending units and whatnot yes I unplug the battery when I did so and in doing so I screwed myself because I never check the codes and it erased the computer in my manual it says that if I unplug the battery I might have to reboot my computer my question being do I have to do that and another question is since my motor is trying to produce spark and fuel could my timing chain be broke and still have the car somewhat turn over and spit whitish grey smoke out of the air intake manifold