Thanks Spartan for quick response.
The fist command worked for me so I didn't tried second option you gave me.

You are right about the start daemon pop up.

Could you please just let me know which apps could be locked. I tried Notes,Sib, filemanager, email, setting, photos and midnight commander. Only conversation worked because that was the first app I locked for experiment but in next attempt when I opened the app and tried to lock above app. it showed lock icon but it is not locked.

Thanks once again