If player A taps his Telekinetic Sliver to tap an opponent's Crimson Hellkite, the opponent can pay 2 red mana (he can pay X, but lets say he pays two) and tap the Crimson Hellkite to put the effect "Crimson Hellkite does two damage to target creature" on the stack.
Now what if a player has a Darkheart Sliver in play and wants to sacrifice his Telekinetic Sliver to gain three life? Can he do it? Does this go on the stack too, and resolve first?
Does the opponent's ability on the stack then fail because there's no target anymore?
Is player A then unable to tap the Crimson Hellkite because it is already tapped?
Is this the correct way to resolve this? If not, what would be the possible scenarios (for simplicity, assume there are only these three creatures in play, no cards left in players's hands and only basic lands on the table)?
I'm a bit confused by this:
"Each player chooses the order in which his or her triggered abilities are put on the stack"*
and I've no idea at all if it applies or not to the above scenario.