"Without a gear being engaged", makes no sense & has nothing to do with making the car move if it's in neutral, only if an input-output brg needle fell in & was jammed between the 2 shafts would the car try to move in neutral. Same with "2 gears at once", the car simply wouldn't move at all, & would stall the engine trying to let the clutch up to move it.
THE INPUT SHAFT IS BEING DRIVEN WITH THE CLUTCH DEPRESSED
1) THE CLUTCH IS NOT BEING RELEASED DUE TO ADJUSTMENT, OR FLEXING/FAILED/WORN/ INCORRECT RELEASE COMPONENTS
2) THE CLUTCH CANNOT BE RELEASED BECAUSE; DISC &/OR COVER ARE WRONG/MISMATCHED; THE HUB IS/WAS DAMAGED & THE DISC IS NOT TRUE ANY LONGER; DISC IS INSTALLED BACKWARDS.
3) SOMETHING OTHER THAN THE DISC IS DRIVING THE INPUT SHAFT; PILOT BUSHING TOO TIGHT/DAMAGED GRABBING INPUT NOSE; SEVERE BELLHOUSING MIS-ALIGNMENT PUTTING A SIDE-LOAD ON & GRABBING INPUT NOSE; USING NON-STOCK FLYWHEEL CAPSCREWS &/OR ADDING WASHERS CAUSING CONTACT WITH DISC HUB.
