One that is not on public roads.
NO
No
About 125cc
no its strictly forbidden because it don't how to sit on motorcycle he will fall or get very scared
A quad. well if you're brave enough, any smaller 2 wheel dirt bike. i mean 14 is old enough to ride a lot of different motor bikes
Quite a bit, depending on where you live, etc. I do not recommend allowing a 16-year-old to ride a motorcycle.
yes. if he's licensed then he can ride it on the street, if he's not licensed he can ride it on private property.
18 to ride it
16
As long as you have a valid motorcycle license you can ride any size bike at any age.
ya 5cc bikes cuz you can get hurt
It differs by country, but typically no. 21 is usually when you're permitted to drive a true motorcycle without any restrictions.