You have an obligation to confess all mortal sins in kind and number. The confessor has an obligation to question you about anything that is not clear. That being said, if you simply say that you played childish pranks, he may not see any reason to question you, when, in fact, you must reveal the entire circumstances and number of times. There is never any harm in making a general confession if you are not scrupulous. In fact, this is highly recommended by spiritual writers, most importantly because many penitents make bad confessions out of lack of knowledge of their obligations. This is true with regard to making a bad examination of conscience especially but also about how to confess properly after making an examination (this is more of a problem from the past 50 years or so; the vast majority of people don’t even know you have to confess the kind of sin with all aggrevating circumstances and the number of times as much as is possible, though this should be taught to children before their first confession). Sorry to digress. Basically, you are in a situation that spiritual authors generally would tell you to make a general confession just to be safe. The reason for this is that as a Catholic you have an obligation to know how to confess your sins properly, and you didn’t do that the first time. This should also be confessed as a sin of neglect, even though it is impossible to know your precise culpability (even for yourself). While it’s possible that you may have no need to make a general confession, there is a lot of reason that you ought to do so, and I think most spiritual authors and moral theologians I have read (and what my own spiritual directors would say) about this case would recommend the same to you. Of course, the general principle is to listen to your spiritual director or confessor, but the problem is that over the past 50 years (and more) many confessors have not received the proper theological training, especially regarding the confessional. We all have heard the terrible things certain members of the hierarchy have said–things that a child could tell you are heretical, such as denying the Resurrection, the necessity of faith to be saved, etc., etc. What most people don’t know is that the proper confessional praxis has suffered at least as much if not more than the dogmatic theology. If you can find a good priest of the Fraternity of St. Peter, for example, I would say that you can trust his judgment, but even they did not all receive sound or sufficient education before the past 5 or 10 years, either. Sorry for the short book as a response, but the short of it is that it simply is the safest thing to do to make a general confession. You will set yourself at ease, and you will not have to worry continually about your state of soul.