[RPG] Do rogues get sneak attack damage added to attacks made outside their turn

You may only apply Sneak Attack once per turn

However, you may apply it whenever you wish in that turn, so long as you meet the conditions:

When you make an attack with a light blade, a hand crossbow, a shortbow, or a sling and hit an enemy granting combat advantage to you, that enemy takes extra damage based on your level (see the Sneak Attack table). You can deal this extra damage only once per turn.

Given that all uses of powers and class features tend to be optional unless otherwise stated, there is no reason why you cannot take SA on either attack. If you have Slaying Action you may apply it on a second action granted by sneak attack. There are a number of powers that grant sneak attack damage as well.

No, because the two conditions do not encompass every possibility.

If the Swashbuckler (S) has interposed himself between an Ally (A) and an Opponent (O). Each occupies a single five by five square.

Such as:
ASO

In this scenario, an ally is within 5 feet from the swashbuckler, but there isn't an ally within 5 feet of the opponent. Lacking an additional effect that will provide advantage to the Swashbuckler, Sneak Attack won't be available.

Similarly, if the Swashbuckler (S) is facing two Opponents (O and X), there are several configurations in which Sneak Attack isn't available.

To summarize, the following conditions will prohibit you from using Sneak Attack, assuming there isn't an external effect providing Advantage.

• Swashbuckler is within 5 feet of more than one hostile creature or character.
• Swashbuckler is attacking the target at melee range and a friendly character or creature is within 5 feet of him but isn't within 5 feet of the target.

Per a twitter post by Jeremy Crawford, Rules as Intended want the Swashbuckler to be within 5 feet of the target. In effect, Rackish Audacity should be written with "except" instead of "other."