SAE 10w30 weight synthetic oil.
to put the oil in the lawnmower's crankcase would be fine, so long as it is an appropriate viscosity.
0.6 litres
If the lawnmower has two compartments one for gas and the other for the oil, then put gas in the gas and a 30w type oil in the oil compartment. Simple as that. If you have an engine with only one compartment then you'll need to check on the manufacturers suggestions which is usually 40:1 or something close.
Drain the oil and gas out of the crankcase and put oil back it should be OK
You get engine damage from lack of lubrication
Drain the oil and catch it in a clean container if you intend on reusing the same oil . Then replace the plug and place the correct amount of oil in the motor.
The engine floods and you have to wait for the lawnmower to drain before you start it up again or it might start smoking.
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.
Yitou can. But its not recommended. It wont run right. Stick with the manufacturers recommended weight.
Most small engines use 30 weight non-detergent type.
Just drain the incorrect oil and re-fill with the correct oil. There shouldn't be any damage unless you ran it for an extended period of time.
No - it is formulated very differently. The crankcase of a four stroke engine needs conventional engine oil. DO NOT use two stroke oil in the crankcase.