Had CH hits yesterday at 3pm, 10:30pm and again at 2am.   None of these were rebounds, but lets just say the beast doesn't like it when you don't allow him to torture you mercilessly.

I have had rebound CH hits after using any type of abortive including O2.  I don't always get them but on occasion I do.

You can usually tell, each person has their own ways of telling if it's a rebound or not.  It's the feel of the hit that is a bit different or the intensity is a bit lower and the timing of the second/rebound hit.

It may take you a bit of time if you are new to CH to figure out when you are having a rebound.  For instance since you asked the question, you could already tell that something was different with your current norm for CH.  The problem is the Beast can change on you in a heart beat so what might be your norm for 1 cycle (if you have them) may change for your next cycle.  Or the change can happen in the current cycle. 

The one thing you will figure out quickly is the beast is a wicked wicked thing.

The only piece of advice I can give is to keep a log and make sure you log how you deal with each hit as well.  Experience and knowledge is the best teacher.