Example b) is a bit of a miswording. Unrevealed cards may not be targeted - period. That was clarified some time ago. Therefore, the only way to target an unrevealed unit is to first spot it. Draw LOS to center of card, ignoring SZ of model (you don't really know it's there, you just think something may be there). If you are within LD (less any modifiers for the unit actually represented by the card), make your spot check. If it is a Flase Lead, or a unit with no SA that allow it to remain hidden (Stalk, Stealth, Lurk, etc.) it is automatically revealed with no need to Spot.
SA's already mentioned, and others like Camo, Smoke and Cover all play a part, here. They reduce the number of inches you must be within, and they penalize the LD check roll.