How can a National Guard officer reclass as a lieutenant, without going to CCC yet?

If you've been to BOLC for transportation then you can go to the CCC of the branch you're wanting. I don't think a 2LT can go to CCC though. That, or I suppose you could go through BOLC of the branch you're wanting. All of that has to be approved by your unit of course.

Get into the slot of the branch you want, the rest is easy.