Is it considered an act of extremism (tanattu') for one who offers financial or in-kind assistance to ask about the reason for his giving—whether he presumes it is due to poverty, destitution, or orphanhood—knowing that I am not poor, destitute, or an orphan in the Shari'ah sense?

If someone is given something without asking for it or desiring it, it is permissible for him to accept it, but not obligatory. The proof for this is the hadith of Umar ibn al-Khattab, may Allah be pleased with him: "Whatever comes to you from this wealth, while you are neither desiring it nor asking for it, then take it; otherwise, do not let your soul hanker after it." The giver should direct the gift to someone who is more in need if the recipient is not in need.