BLF in "deviceanduser" mode

I read posts about set up BLF for extension and excited about the potential of BLF. Before I buy a BLF voip phone set, I have a question: does the BLF works in "deviceanduser" mode? For example, I have:

device name = desk
device # = 112
this device belongs to the user:
user name = John
user extension # =400
my trixbox server is 192.168.0.150

On the VOIP phone set,
if I like the BLF to point to a device, do I write this?
Unit 1 Key 1: fnc=blf+sd;sub=112@192.168.0.150;nme=desk

if I like the BLF points to the user, do I write this?
Unit 1 Key 2: fnc=blf+sd;sub=400@192.168.0.150;nme=John

furthermore, if my conference room name = general and conference room # = 900
if I like the BLF points to the conference room, do I write this:
Unit 1 Key 3: fnc=blf+sd;sub=900@192.168.0.150;nme=general

Does this work for any destination that has a extension number like Ring groups, paging groups?

Many thanks.