Perhaps it is the starter drive. That happened to my riding mower. Got the drive replaced, works fine.
i dont see why not.
Magnetos
probably
the magneto
No for your lawn mower you will just need regular lawn mower oil.
Yes. Just make sure to use a battery of the same voltage.
I'm assuming its a riding lawn mower of some type. Our own lawn mowers of this type have an alternator in them that keeps the battery charged
replace it
a rider will or an electric start will.
totally
Dead cell in battery, loose of corroded battery connections, or the charging system on the mower engine is defective.
This depends on the mower. With out knowing the make and model of the mower so I can look up the type of battery this question can not be answered