Cutting off the air from the hose?
 

I stood on the hose, but it only triggers Doc trying to tell you to stop. The hints tell me to do this so I am confused, what am I supposed to be doing?

Go into the future, the old fashioned way


Just wait a little bit, after a while the gears will mysteriously become "unstuck" and doc will free his young self.

just wait loooong time...