Is it permissible for someone who does not adhere to a specific madhhab to adopt jurisprudential opinions that suit their particular issue, without being bound by a single madhhab, and without merely seeking out concessions or following personal whims, and to act upon the opinions they have chosen without resorting to a fatwa, relying instead on their own research and their preference for a particular evidence and the view of its proponent? And would they fall into the forbidden if they were to follow the opinion of Ibn Taymiyyah after preferring it in a matter of divorce, or the opinion of Ibn Hazm regarding the issue of commencing the waiting period (iddah)?

There is no harm for a common person to act upon the opinion of a trustworthy scholar, as long as they are confident in the correctness of their statement, and are not following their whims or seeking out dispensations. They may seek a fatwa from whomever they wish, without picking and choosing dispensations. If scholars differ, and if the common person's intellect and understanding are expansive enough, they should inquire about their doctrines and proofs and adopt what they deem most probable. If their understanding is limited, it is permissible for them to imitate whomever they consider best. In the aforementioned matters of divorce, the fatwa is given according to the opinion of the majority of scholars, and no one is to be criticized for adopting the view of other mujtahid imams. However, it is not advisable to follow Ibn Hazm's opinion regarding the non-occurrence of conditional divorce when divorce is intended by it.