Last year in Team Fortress 2, there was a random occurrence that you would get a Naughty or Nice Winter crate, which you could unlock with a specific key for that. This year, I have almost a full page of mixed naughty and nice crates, and I did get all of them this year, but noticed that in the shop there was no key for those crates. Are the keys available later or is it just an ordinary key that you buy?
The keys probably are not on sale yet. You will have to wait a little bit untail they are on the team fortress item store. It will probably say new on the store tab when you launch team fortress and then buy them for $2.50 each. So just wait a little bit.
Honestly, I would trade them. Seeing as many people would want them before the keys come out, so they can get unusual hats/strange weapons, I would sell them for about a reclaimed metal each on http://www.tf2outpost.com or http://www.trade.tf. Many people love festive items, and this is time to sell your unwanted crates.
Nothing. You cannot unbox those crates anymore, as the 2013 Winter Event has already expired.
If I found a crate in Team Fortress 2 and open it with a key, can I trade or craft the item stored inside?
Yes, crate-opened items can be crafted or traded.
The only items not craftable or tradeable (excluding event or limited edition items) are those bought directly from the store.
If items bought from the store could be traded and crafted, there is a possibility of massive, massive inflation on the item economy. Hence, the ban.