Keys

Thanks, I've picked up the Pirates of Black Cove key.

No you cannot give away keys that were once free, even if you bought them afterwards.
However you can share them just like you did with the both above.

No

If it's in the list of choices when you go to make a giveaway, then yes. If it doesn't show up there, then no.

If it was given away for free and/or it's not in the giveaway list (the list that appears when you start typing the title of the game in the giveaway creation page), no, you can't create a giveaway for it.

Games massively given away for free are removed from the list, and you shouldn't make giveaways for those while they're not in the list either (there's a delay until they're removed from it by the staff).

Not really, once a game hits the "Given out for free" list, it becomes ineligible to make giveaways of it for an indeterminately long time. The only thing you can really do is hand them out personally or drop them on forums.

Edit: Geez, I'm not even sure why I bother. :S

Even if you want to do it, you can't do it.
Btw thanks for the key, got the 2nd.