How long will i have a hard cast for a non-displaced fibula fracture?

It depends: It takes 8 weeks for bone to heal in a healthy person who does not smoke. A non-displaced fracture could be put into a cast or a walking boot, depending how stable it is. A conservative physician would have you in one for 6 to 8 weeks. More aggressive would be for 2 to 4 week and then transition to a boot when an xray shows good callus formation at the fracture site.

Depends: If your inner ankle doesn't hurt this may be a stable brake and some would put you in a walking boot immediately. Some docs may error on the side of caution or if you tore the inner deltoid ligament a cast will help stabilize things and is usually used for 4-6 weeks.