Does divine justice manifest itself in granting Iblis respite until the Day of Judgment, followed by his entry into Hellfire, while humans live a short life and then are eternally consigned to Hellfire?

Doubting God's justice is disbelief (kufr), and the one who doubts must renew his Islam. Allah does what He wills and wrongs no one. Iblis rejected God's command and was arrogant; he did not repent, but rather persisted in his disbelief and asked for respite to mislead humankind. So Allah granted him that for a wisdom. Iblis cannot repent, for Allah has decreed upon him the curse and the Fire. Iblis remaining alive until the Day of Judgment is for a wisdom, and this is not an injustice, but rather the recompense for his rebellion. Disbelievers vary in their torment according to the duration of their disbelief, and every disbeliever will have a lighter torment than Iblis. It is advised to avoid such doubts and to busy oneself with worship.