This Bulbapedia article and this Smogon post say conflicting things about SOS mechanics.
If a call was made and unanswered in the previous turn, does the success rate increase 3 times or 4.5 times?
Does the super effective multiplier only take the previous one turn into consideration, or all earlier turns? Does it apply if the ally was hit by a super effective attack, survived, and was knocked out by something else? Is it a 2x multiplier or a 3x multiplier?
Are the answers different for SM and USM?
Please don't question my curiosity.