NIST SP 800-20 Appendix A has what presumably are supposed to be test vectors for 3DES except almost all of the test vectors utilize 8-byte keys and not the 24-byte keys that 3DES is supposed to have. See, for example, table's A.2, A.3, A.4, A.8 and A.10. So what's the point? These test vectors don't seem like they're testing what they ought to be testing.
It is for the 1st version of 3DES which is only using the same key three times (3DES-EDE1)
Which is equivalent to DES (I think they did that so you could use 3DES to exchange with someone using DES).
There are 3 different versions (or ways of using DES). EDE3 is the strongest with 3 different keys being used.