Your answer depends on who owns the driveway, and who damaged the drain. Best practices dictate that you file a police report and contact your insurance carrier, who can sort out who pays for the repair of the damage.
drain and then into the rivers
Yes.
The renter is fully responsible for all damages
Yes. Both caustic and acid based drain cleaners can do damage to your metal pipes. Instead, you can try an all natural remedy of pouring baking soda down the drain followed by vinegar.
Its Mold, they all do it when they drain on concrete. Just go to local market and pick up some outdoor mold treament keep away from children and pets.
Drain it and cover it from the direct frost.
The purpose of a French drain is to move water away from your home, protecting it from water damage. You can learn more about french drains at the Wikipedia.
drain all of it out. hopefully there will be no damage to the rubber components.
Yes. Suggest you inspect pool and drain closely for cracks or other damage.
It must be at bottom of the radiator, you should a valve responsible for drainage.
The property owner is totally responsible
Look at the stats: Magical Leaf - 60 Damage/20 PP Giga Drain - 60 Damage/10 PP, plus 50% of damage done is added to your Pokemon. Personally I would always go for Magical Leaf due to it's better PP, but it depends on your battle style.