Is it obligatory for a woman to observe the iddah (waiting period) if her husband deserted her for many months and then the judge divorced her with an irrevocable divorce? And what is the preferred and less preferred opinion on this issue?

The waiting period (iddah) is obligatory for a divorced woman with whom consummation has occurred, or for a woman whose husband has died. Her iddah is not waived if her husband abandoned her for the duration of the iddah or more before the divorce. She must observe the iddah once the divorce takes place.