If the clutch is stuck (rusted to the flywheel) the car should start normally, or at least turn over, with the transmission in neutral, but it will then be impossible to shift gears, because the clutch will not release.

If the car rolls freely with the transmission in neutral, but will not move with it in gear, and when you get the car moving with the clutch depressed, the rear tires lock up when you let it out, the engine is stuck. Even if the clutch is stuck, you should be able to turn the engine with a breaker bar on the crankshaft nut, if it is in neutral.

Actually, I should say "probably stuck" because it could be something else. Many years ago, a friend had a Fiat Spider that had sat for some time, and he asked me to help him get it running. It would not turn over. We tried all kinds of stuff---popping the clutch in gear, breaker bar on the crankshaft nut, a whole can of WD40 down the plug holes........nothing would get it to move. Just as we were about to give up, I had an inspiration. I took a knife and cut the belt off of the air pump, at which point it turned easily. Started right up too, after we put the plugs back in and fed it some fresh gas. Belched out a huge cloud of white smoke (all that WD had to go some where) then ran pretty much normally. Moral of the story---check for a seized AC compressor, alternator, water pump, or whatever before you give up on it.