Hold back to kill?

I would like to check if this app (http://forum.xda-developers.com/andr...-kill-t3039412) would work on rooted G Flex 2? This is one of the main features I would use with root, so I would like to check if this is possible before purchasing the phone?

EDIT: I understand that dual window clashes with the back command, so does disabling dual window helped? Thanks.