Why do we sit in a circle at the Breaking of Bread meeting?
This is a question for which there is not a simple Biblical reference of chapter and verse as to order. However, we do find that there are references that shed light on the answer as well as principles that God has given us in His Word. For example, we do not have the specific instruction to use a gospel hymn in the opening of a gospel meeting or at the end. However, the Spirit of God, through the Apostle Paul, encourages us in the use of "psalms and hymns and spiritual songs" (Col 3:16; Eph 5:19). We all would agree that a suitable hymn at the beginning of a gospel meeting can help set the tone; as well, a proper closing hymn can confirm the message. Coupled with this is the instruction to the Corinthian church "let all things be done decently and in order" (1Cor 14:40).
The Lord Himself instituted the remembrance meeting and we see it practiced in the Acts, with complementary teaching in the epistles in connection with this high privilege. However, the physical direction of the order of sitting is not spelled out. But we do have a very detailed cameo, or illustration, first given to the nation of Israel when God revealed that He would presence Himself among them. It is found in the Tabernacle. God gave very specific instructions regarding where the people would locate in regard to God being in their midst in the Tabernacle. The physical Tabernacle was to be in the center of the encamped nation and each tribe was to have a specific location for the pitching of their tents, in a circular manner that surrounded the whole tabernacle (Num 2). The Tabernacle and all it enclosed was in the midst of the camp and observed by the nations that did not have access.
When we turn our attention to the record of Revelation 4 and 5 we view the scene of a throne and "in the midst a Lamb as it had been slain" (Rev 5:6). In the chapters describing this scene we have the words repeated "round about" which suggests encircled. So when we consider Gods detailed plans for a nation regarding the order for appreciation for His meeting place and then consider His unfolding of a place of unhindered worship we find that "in the midst," encircled, seems to be an order that is in the purpose of God.
From a practical standpoint it has merit over a congregational arrangement of rows of seats that put many from a distance looking at the back of heads, not hearing the one leading in worship because they are looking forward, and possibly not observing the simple table with the bread and wine. The circle or square seems to alleviate some of these distractions. Also, it aids in distinguishing the place of the "unlearned or unbeliever" that Paul refers to in 1 Corinthians 14:23. From these abbreviated remarks I think you will see that the order, although simple, has merits that assist us in our concentration and desire to remember the One in our midst.
Would it be in order for a young believer, not in fellowship, to publically ask a question at the assembly Bible Reading?
This is a question that we would not answer as dogma. We believe that this is best addressed by the elders in a local assembly. I assume that the questioner is addressing a regular assembly Bible reading. It would be preferable not to open the questioning as if it is open to all. There may be visitors present that may be or may not be saved and some of their questions could be far off the subject and cause disruption. It would be preferable for older men to instruct younger men and older sisters to instruct younger sisters in a one-on-one way as Paul exhorts Titus (Titus 2:1-8).
However, another alternative would be to provide, in an available location, question cards, for the Bible readings, that can be passed on to those that have the responsibility to lead the reading. These questions could come from male or female and could be anonymous. The questions could also be reviewed for their suitability before the next public meeting. We would refer to 1 Corinthians 14:40, "let all things be done decently and in order." Let us seek to maintain an atmosphere of reverence in our gatherings when the world around us has gone casual and in many ways disrespectful towards the Word of God.