Remember that one of the things that everyone had to do during the Feast of Tabernacle season was to confess, so these questions that Alma was asking may have had something to do with helping people to be introspective, to repent, to recognize what they needed to do as a part of preparing themselves for the covenant to be renewed. This was so that the Day of Atonement could be celebrated properly, so that the blood of the sacrifice would purify and cleanse everyone and wash their garments clean. Are those all phrases in Alma 5? You bet. So, in Alma 5, again we are going to another level of why it is a great speech. It taps into all of the really fundamental concepts of ancient Israelite religion, the revealed law that they were living (and supposed to be) keeping. Indeed, it taps into the Law of Moses as revealed by Moses.
Moreover, Alma’s questions were drawn directly from his experiences. He knew what he was talking about. Another way that we teach with the Spirit is when we talk about things that we "know whereof we speak." When he asked "have you had his image on your countenance?" or when he asked about being born of God, he had experience in these areas. He asked about being born again, and undoubtedly as people heard him asking those questions, they knew and accepted what he was saying because they knew his story. They had probably heard it many times and they knew how sincere he was about these things.
Book of Mormon Central "Why Did Alma Ask Church Members Fifty Probing Questions?" KnoWhy 112 (June 1, 2016)