If a young man age 31, has Down Syndrome, but is high functioning, can he be babtised and confirmed into the chuch?
the level at which this gentleman functions is not the issue. All children born to Catholic parents have the right to the sacraments of initiation and it is the responsibility of the parents to have them baptized and confirmed. Particularly in the case of Downs or other condition where related health issues my shorten life expectancy, Confirmation should not be delayed. There is no canonical or theological bar to the sacraments for this person. If he is able, an in the judgement of the pastor and those who care for him, to participate in a preparation class and benefit from it, he should certainly be included, with appropriate help and assistance but there is no requirement beyond the desire for the sacraments.
As far as confession and First Communion, he should be prepared in the same manner as any one else, child or adult, who functions at his level, and the expectations tailored for his condition and understanding. It is enough that he understand the difference between ordinary food and the Eucharist, and that he express, any way he can even if not verbally, a love of Christ and a desire to receive Jesus.
the US Bishops have a pastoral letter on this topic. No one may denied the sacraments on such a basis if otherwise they are not barred from the sacraments. It is up to the pastor to judge if this individual is capable of the intent and knowledge necessary to commit a sin, and whether he needs confession. No catechist, parent or DRE may make that decision, although they can advise the priest about the person’s background.