Is the father entitled to retract his promise to his deceased son that he would own two rooms in his house, and to dispose of them to another son? And does the divorced wife of the deceased son or his children inherit anything from that?

If what occurred from the father was merely a promise to his son regarding the two rooms, and it was not fulfilled, then it is not considered a gift (hibah (definition)). However, if the gift was completed with its conditions during the son's lifetime, such that the father relinquished control over them and the son lived in them or disposed of them as an owner, then the gift is binding, and the father does not have the right to revoke it after the son's death. Therefore, if the gift was completed, the son's heirs are the most entitled to the two rooms, and they are his children, his father, and his mother (if she is alive), and his divorced wife has no right to them. But if the gift was merely a promise, then the father has the right to dispose of them because they have not exited his ownership.