Need some help to find out what the fault is.

I was on the motorway in 4th gear going between 50/60mph and i took it to about 5800rpm and tryed to change in to 5th gear, crunch would not go in to gear. Slowed down tryed to drop it back in to 4th would not go in double clutched it went in to 4th 4000rpm now tryed to change up to 5th again would not go in but went back in to 4th.
stopped at service station as i was slowing down it crunched again in 2nd.
Checked if it would go into gear as the car was stationery. Now went into all gears no problems.
Praying left service station back on motorway changing gears no problem keeping revs under 4000rpm.
Now on my way back thought let me try up the revs and change in to 5th problem was back. Pulled over car would not go into 1st or 2nd now. worked my way back from 5th to 1st went into all gears but 1st and 2nd very stiff.

Thank you in advance.

As far as I know, all Imprezas are Hydraulic clutch!!
Sounds more serious than that!

So is it definetly my gearbox?

B16....It could be a few things,Has the master cylinder seals got weak,Not giving the correct clutch clearance.....?.
Is there any wet patches under the car where the gearbox meets the engine....???AS i have known gearbox/engine oil seals weep into the clutch,And getting onto the friction plate,Making the plate not clear(sticking to the flywheel)...?.
A gearbox fault....???
I would try burning the clutch,And see if the symptoms become any better...This can be done by...Putting on the handbrake as firmly as possable,And trying to pull away in second gear...Keeping the revs up,Whilst,Slipping the clutch...This thumps heat into the plate and chars any oil remnants thats contaminating it.....
The reason you could get the gears whilst dropping the revs,Could indicate you are "Matching" the revolutions for the gear clusters to mesh....I would try that first......And decide from there on..
Hopefully its not a gearbox problem for you..Good luck...kev.

Firstly thanks for the replys.
I have not had a chance to check under the car yet but will do so tomorrro.
Secondly would like to ask if a legacy gearbox would fit in my95 wrx?