Is it permissible to adopt the view of those who say that an innovative (bid'i) divorce does not take effect, and how is a Sunnah (according to the prophetic tradition) divorce for a woman whose menstruation is irregular?

If you possess the ability to understand and comprehend the Sharia evidence and to weigh between different rulings, then there is no harm for you in adopting what you find most preponderant among the sayings of the scholars. However, if you do not possess this ability, and you are a common person, then it is your duty to ask trustworthy scholars and act upon their fatwa, as Allah Almighty says: "So ask the people of the message if you do not know."

As for the divorce of a woman with an irregular menstrual cycle, there is no issue with it. She is considered pure as long as menstruation has not come to her, and divorcing her during this period is considered a Sunnah divorce if her husband has not had intercourse with her during that period.