Depends on the output of the charger which you did not list. A dead battery can be recharged with a 10 amp charger in 3 hours.
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
the magneto
yes.
totally
No, it is not necessary to remove it. You can charge it right there on the mower.
12 volt
replace it
price
Not at all. A 35 amp charger is far too large to charge a lawn mower battery. Use a 10 amp automatic charger.
yes as long as it is not totally dead.
no
NO You have to many AMPS from a car, you can jump start it butdon't charge it.