You can NOT flash U1 firmware after Unlock your phone by SamKEY SPR, Phone will be RELOCKED !
You can NOT Flash A102U > A102U1
You can NOT Flash A205U > A205U1
You can NOT Flash A505U > A505U1
You can NOT Flash A515U > A515U1
If you flash U > U1 ,,, then it might get relocked after unlock!