Is a young man who committed sins and uttered the Shahada before his death considered a Muslim for whom charity and supplication are permissible, or does his denial of the prohibition of music and his justification of some forbidden things make him an infidel?

Drinking alcohol and using drugs are major sins, but they do not amount to major disbelief (kufr akbar). The statement that singing is not forbidden does not necessitate disbelief, due to the existence of differing opinions, interpretations, and ignorance on the matter. As for the person's statement about hashish, it is not an explicit declaration of permissibility, and a Muslim should not be declared a disbeliever if there is doubt. A person who abandons prayer is not judged to be a disbeliever unless they abandon it completely; one who prays sometimes is committing a major sin. There is no impediment to supplicating for him and giving charity on his behalf, especially since his life concluded with the declaration of Tawhid (definition) (monotheism), for the Prophet, peace and blessings be upon him, said: "Whoever’s last words are ‘Lā ilāha illallāh’ (There is no god but Allah) will enter Paradise."