Factory Data Reset and Hard Reset problem

Hello , i got an SM-T550X ( the Demo version ) , i flashed a Stock ROM , but now i can't do a hard/factory reset , i tried with CWM recovery but nothing happens .
The Error message from stock recovery is es not allow factory reset.
and via CWM recovery
E: Can't open /cache/recovery/log
W:failed to mount /dev/block/mtdblock2 (Block device required)..


Thanks for your help (and sorry for bad English :p )