What is the ruling on one who thought, before reaching puberty, that Allah might do something without wisdom, and this belief continued with him until after reaching puberty?

The statement that Allah Almighty might do something without wisdom is a grave error and contrary to explicit texts and the belief of the Ahl al-Sunnah. Allah has described Himself as All-Wise in many places in His Book. Any action that proceeds without wisdom is frivolous, and He, glory be to Him, has absolved Himself from frivolity and play. It is obligatory for the accountable person to believe in Allah Almighty's wisdom in all that He legislates and decrees, whether that wisdom is apparent or not. As for what occurred before accountability, one is not held responsible for it.