Is it permissible for God to favor one person over another through intercession or because of deeds dedicated to Him, and how does that align with God's justice, knowing that people are favored based on piety?

A servant may attain higher ranks in Paradise than others, even if the latter were more pious, due to certain reasons. Among them: Allah may ordain for him righteous children or loyal friends who give charity, perform Hajj on his behalf, dedicate the reward of good deeds to him, or intercede for him after Allah's permission. This does not contradict Allah's justice. We should strive in good deeds and acquire deep understanding of the religion, and abandon concern for assumptions that do not lead to action.