Yaaleh Veyavo in Bentching

If one forgets Ya’aleh Veyavo in bentching, but remembers before saying Hashem’s name at Bonei Yerushalayim, he goes back. If one remembered after that, but before beginning the next Brocho, he recites the extra Brocho as printed in the Bentcher. If one already began even the first word (Boruch) of the next Brocho, one must begin bentching again if it is Yom Tov, but not if it is Chol Hamoied.

On Yom Tov, the Horachamon for both Yom Tov and Sukkos are recited, in that order. On Chol Hamoied, only the Horachamon for Sukkos is recited.