What is the ruling on the Aqiqah if a calf was slaughtered with the intention of Aqiqah for seven people, and the butcher confirmed that it met the conditions in terms of age, but it later became clear that it was less than two years old?

There are three issues here: First, the permissibility of performing aqiqah (definition) for oneself and for one's adult wife. Second, the permissibility, according to the Shafiis, of slaughtering a cow for aqiqah on behalf of more than one person, by analogy with Eid sacrifice (udhiyah (definition)), and their opinion holds strong. Third, the aqiqah requires the same conditions as the Eid sacrifice in terms of age and freedom from defects. If the slaughtered animal does not meet the conditions, it is considered meat given in charity and is not sufficient for aqiqah. If you have doubts and the trustworthy butcher confirms it, you may accept his word.