1 May 2006
You choose the value of X as Squealing Devil's ability resolves. X can be 0.
1 May 2006
For this creature to not be sacrificed, {B} must have been spent on the {1}{R} mana cost. It doesn't matter if {B} is spent on {X}.
1 May 2006
If this enters in a way other than announcing it as a spell, then the appropriate mana can't have been paid, and you'll have to sacrifice it.