A clutch pedal that won’t return is either sticking (due to friction) has a broken or weak return spring or is throwing out beyond the point it should (like an athlete hyper-extending their knee). How that’s related to the gear-lever locking up is anybody’s guess, but it’s true that if the clutch isn’t disengaging properly (which could be the case if the clutch pedal isn’t doing its thing properly) then the car will refuse to select gears and that can feel like the lever is jammed. Switch the engine off and see if the gears will then select. If so, I’d say the clutch is not disengaging and you may have to pull it all apart again to find out why.
