During a criminal trial, is the accused allowed to testify "I said such and such/I told him such and such"?

Allowed? Sure but many attorneys don't want the defendant (accused) to testify at their criminal trial since the prosecution can then ask them all sorts of things. I rarely hear of the defendant testifying. Remember, you are testifying under "penalty of perjury" and that's a MAJOR crime. Even if you are innocent, they can still twist things around.