OpenGL,GameProgramming tips?

Hey, got some general questions about gameprogramming wiht openGL:

I have a Stickman riding on a BMX/DirtBike and has to jump over a jump.
The stickman is riding on a Line/Track(Curvy)…

-> How would you make this with OpenGL that the rider is riding on this line?
My idea would be that the rider isnt really riding on the line(line is just background), and the stickman just will be moved by an mathematic function.(so no gravity)
better ideas?

2)3D Programming OpenGL:
What if I Have a 3D Stickman(made with Blender) or something else, which should walk on my 3D modeled World.
How would you do this, that the stickman runs over the 3d area(has rough ground,and stickman can run up a hill?).?