Could you post photos?

Ok. I'm pretty sure the yellow parts are rotted. It's weird because
the "rot" is much worse on one side. The surface where its yellow can
be scratched off, but it's not "squishy". I wasn't sure if I can cut it
there on the trunk though. The other side looks normal and green.

Hang in there, buddy! Momma loves you.

In the first photo. Showing the yellowing on the lower trunk. I would just watch for anything questionable (squishy and darkening).

In this same photo. The top branches, would concern me with the outer bark of the branches dying off. If this is dry and hard, then not an issue. If it is soft and continues, then you will need to cut back until the inner cambium layer which should be white and with no beige spots/marks within it.

Not sure what the yellowing is. Looks similar to sun burn on the caudex, but possibly a burn from frost is similar in appearance. I would think that it would become soft and blackened if frozen?

I have not had an experience with adeniums being hit with frost.

Rick

The yellow part is just scarring, Wendy. I have a plant with similar discoloration and it also feels firm underneath so I just left it alone. Dramatically disfigured but otherwise healthy and a profuse bloomer.