No. You don't have to exert as much force since you're really just moving your legs up and down and aren't propelling yourself forward. Try a treadmill at a slight incline for a better simulation....
The only way to get better at running is by running. If you're injured or unable to run for other reasons, you can maintain decent fitness and leg strength through cycling, swimming, stair-climbing,...
They mean different things. "When" = "at the time that." "While" = "during the time that." Did you lose weight when you were running every day? You must carry water with you when you are running long...
"Rich" and "lean" refer to the air/fuel mixture. Rich means a higher proportion of fuel than is needed and lean means less. An overly rich mixture can foul plugs, cause sluggish performance and...