Can AN EXECUTOR OF AN IRREVOCABLE TRUST PASS RESPONSIBILITY TO ANOTHER PERSON NOT LISTED AS A HEIR?

Answer 1

Yes actually the executor may do so indeed so long as there is no issue that contests it (or other party of interest). Your heirs are as follows (and in this order):
Spouse and Children; Parents; Other relatives (also called Collaterals). If none of those contest it, then the executor may pass the trust to another person. HOWEVER, it depends on how it is written if the issue of the person that the trust is transferred to may collect at that person's death or if it goes back to the beginning and starts all over again.

Answer 2

Yes, provided those who have equal right to administer the estate consent.