At what time did you make the appointment with the hospital?
ご質問ありがとうございます。
「病院の予約は何時?」の場合は①の"What time is the hospital appointment?"又は、"What time is the appointment at the hospital?"と言えます。
「何時に病院の予約をした?」は②の"At what time did you make the appointment with the hospital?"、又は"For what time did you make the appointment with the hospital?"
ご参考に。