Why can't clutch pedal be depressed?

so , it seems the engine does start in gear, with clutch depressed.
or cranks , brakes off, and car does not move. with clutch depressed, if yes, then the clutch is not 100% seized.
we now know the trans is in neutral (could be siezed check its Gear lub levels?)

I can not decode, stuck in gear. elaborate that.
nor "
"still stuck"
the only clue here, is
"stalls when clutch is let out."

this last statement makes me presume you depressed the clutch
then turn the key to start, it started
and when you let the clutch out, the engine stalls
does it do that rear wheels (2wd mode) ? lift driving wheels off the ground.... (these proves engine not weak)
yes, transmission is sized.
no, then it is stuck in gear.

Suspect the clutch is frozen and even when you press the pedal it does not disengage. If it shifts into other gears without the engine running. you will need to break the clutch free. Put it is high gear with the clutch depressed and rock the car back and forth with a bunch of friends pushing on it.

You Have a broken shifting yolk inside the transmission

Clutch hydraulics has air in it or the clutch master cylinder is failing.

Clutch plate and pressure plate seem to be too weak to pull the car. Or one of the CV joints is detached from the gear box. To test the clutch plate, park the car on flat surface. Pull the hand brake up, start the car, depress the foot brake pedal, depress the clutch pedal, put the car in 1st gear, press the gas pedal and leave the clutch pedal at once, while keeping the brake pedal depressed.
Follow one of the two following statements:
1. Engine does not shut down and remain start. (Clutch plate, pressure plate and clutch bearing defective - Replace all as a set)
2. Engine shuts down. (Clutch system is OK and does not require any repair).

Clutch plate and pressure plate seem to be too weak to pull the car. To test the clutch plate, park the car on flat surface. Pull the hand brake up, start the car, depress the foot brake pedal, depress the clutch pedal, put the car in 1st gear, press the gas pedal and leave the clutch pedal at once, while keeping the brake pedal depressed.
Follow one of the two following statements:
1. Engine does not shut down and remain start. (Clutch plate, pressure plate and clutch bearing defective - Replace all as a set)
2. Engine shuts down. (Clutch system is OK and does not require any repair).

The pedal return spring should be checked. Also the pedal bushings where pedal connects to the pedal support up under dash may be worn and not allowing free pedal movement. Work the pedal with your hand and watch the upper mounting of the pedal to see if you can see the problem. I would expect the bushings need replaced. You might try a little light oil where the clutch pedal attaches.

look under your dash driverside at your clutch pedal and there should be an arm that goes through the firewall and to your pedal if it is disconected reconect it if not then check your clutch fluid

Hi:
You need to check your clutch master cylinder reservour, not your brake cylinder. It is located approx in front of the clutch pedal, outboard of the brake cylinder. If it is low, you need to inspect for leaks around it, the lines connecting it to the clutch slave cylinder that is mounted on the transmission.

how does the clutch pedal feel?..clutch out of adjustment,needs clutch job...kev-mn.