Besides the obvious (don't go around shooting random people, airsoft on public or private property without permission, painting the orange tip of the gun, etc.), no.
yes airsoft guns are legal in OHIO
Yes, airsoft guns are legal in Canada.
Usually airsoft guns aren't allowed in public places
Yes, they are.
Yes
Yes they are.
Yes
Yes
Yes, i'm 14 and i own 4 airsoft guns.. As long as its on your property and not like in a city
18 in the USA
I don't know about Canadian airsoft stores, but I know that most airsoft in North America sell Canadian-legal airsoft guns.
You will have to check the law in India regarding Airsoft guns. Until you are 100% sure they are legal, do not bring them to India.