How many limited-time quest-rewards have already passed?

[Enkidoh]

Well, there's been at least three seperate seasonal events which have come and gone since launch - a very late Summer event (Moonfire Faire), which had new and old 1.0 swimwear, the Halloween event (All Saints Eve) which had ghost costumes and Halloween inspired food items along with the Pumpkin head costume headgear from 1.0, and finally, most recently, the Christmas event (the Starlight Celebration) which had snowman costumes and Santa sleigh barding for your chocobo plus the Santa and reindeer costumes from 1.0. All these events are classed as 'seasonal', so they should all return (with new items plus the old ones for sale) when the time comes.

The only other special event that happened was the FFXIII Lightning event which gave players Lightning and Snow costumes plus FFXIII/XIII-2 themed weapons, but that should be returning in February to coincide with the international release of Lightning Returns. So you'll have a chance to do that.

Other than these events, the only other 'bonus items'/rewards that were formerly offered but are now unavailable are mostly related to version 1.0, specifically the Legacy Campaign (special chocobo mount, name in credits), or items and achievements that were only offered in 1.0 and are now unattainable, like the Hermes Shoes and the Gobbuue Mount. SE have stated these will never be available again, so sadly if you didn't have 1.0 and gained them then, you're out of luck I'm sorry to say.