Is it permissible to purchase airline tickets at a reduced price using a special code designated for people with disabilities, when the person is not among them? And is the intention for 'Umrah considered pure if it includes visiting relatives and staying with them for 9 days?

If the reduced travel tickets are specifically for people with special needs, and this description does not apply to the questioner, then it is not permissible for him to take these reduced tickets. This is because it is considered consuming people's wealth unlawfully, as Allah Almighty says: "And do not consume your properties among yourselves wrongfully." It is also not permissible for others to assist him in this, as it is cooperation in sin and aggression, as Allah Almighty says: "And do not cooperate in sin and aggression." As for the intention to travel for 'Umrah and then visit one's brother, this does not make the intention impure for Allah Almighty; rather, it combines 'Umrah with maintaining kinship ties, which increases the reward and recompense.