You have a mess.
You get engine damage from lack of lubrication
Someone put it there.
it smokes out the exhaust...
Apparently you didn't crank it up. You are still here. Nothing except it may clean out some old dirty oil. Remove the gas and the oil and discard same. Refill the oil section and refill the gas tank. Don't do that again.
Putting gas into the oil of a 4-stroke ATV, and running it can cause damage if oil is diluted enough. Gas is not a lubricant and bearing/cylinder wall damage can occur. drain the oil and refill with clean oil.
Will damage the engine very quick. Remove asap and flush with at least a quart of oil. Then refill.
Someone probably put sugar in your gas tank.
A pint or less mixing with a full tank of gasoline, nothing will happen.
A small amount like 10 ounces to a full tank of gas will not be a problem. Next time read the directions.
If all oil the mower will not start. If only a little oil, the mower may start but run rough and smoke very much.
nothing