Find out which keying option is being used in Triple DES?
Actually, there's no known way (assuming practical amounts of computing power) to distinguish keying methods 1 and 2.  You mention a "brute-force attack of complexity $O(2^{56})$ followed by a chosen plaintext attack of complexity $O(2^{57})$", there's no obvious way to frame an attack against either of the first two options in this matter; you can't do a brute force attack on one of the keys, because there's no obvious way to confirm a guess on a potential key (other than immediately doing a brute force attack on another of the keys, in which case you're really talking about an effort of $O(2^{112})$.

On the other hand, it is feasible (if moderately difficult) to distinguish the third option from the other two.  This third option is essentially DES; a brute force search of all possible $2^{56}$ DES keys will distinguish it given a single plaintext/ciphertext pair.  In addition, with sufficient known plaintext/ciphertext, linear cryptanalysis can make the distinguishing effort moderately easier.

The best work I known on linear cryptanalysis is this paper; using approximately $2^{43}$ plaintext/ciphertext pairs (that is, a few trillion), they are able to distinguish DES from a random permutation with about $O(2^{39})$ DES computations, which is moderately cheaper than simple brute force.