I'm not aware of any arming function on 744 engine squibs (not electrically, anyway).
Pulling the fire handle, however, may allow you to turn the handle afterwards (e.g. some kind of mechanical interlock, like sticking a key in a lock and turning it)
Rgds
NSEU
P.S. A good test for a desktop simulator:
On the real aircraft, you can only pull the fire handle out if:
1) The respective fuel cutoff lever is in OFF, or
2) The fuel cutoff lever is in RUN and, at the same time, a fire has been detected, or
3) You use the hidden mechanical override button behind the handle (at any time)