Only if there were a fault that kept the disc from disengaging the flywheel, like if something bent which wouldn't allow the fingers on the pressure plate to move. But it slipping, no, if anything it would make it easier to go in gear.

 

Most definitely. If the clutch cable wasnt adjusted properly over the course of life of the clutch, by the time it gets real thin the adjustment will barely suffice and you won't fully release. This would be evident in the clutch pedal operation though, you'd likely notice it grabbing higher and higher.