There is not any age limit as such, but you would need to get the finance to pay for the film and few producers would be likely to back someone very young.
Young people would be most likely to lobby for money to pay for college.
Yes, a young river typically erodes more than an old river because young rivers have a steeper gradient, higher energy, and are still shaping their course. Over time, old rivers tend to have a more established path with reduced erosional power.
Young people and their parents would likely lobby the government for money for college.
The young readers' books most likely to have bibliographies are, in no particular order, history books, science books, and biographies. Textbooks would also be likely t have bibiliogrphies.
young river
The speeds of river vary so much, even on individual river, that any attempt to answer this would devolve into nonsense.
Young people and their parents
A young man who feels confused about his life
Young people and their parents
brave
A river is young if it has an oxbow lake. Erosion and deposits of soil cause crescent shaped oxbow lakes along a river and change the river's course.