Hey there! I think you'll be interested in my answer to the recent question about how a priest in 1999 and and medieval priest would disagree with each other.

Yes, the question asks about priests, but my answer focuses on the biggest difference being the relationship of the Church/clergy to normal ol' lay people.

I hope this helps!

I can only really elaborate on that of Orthodox Christianity, which mostly means the Eastern Roman Empire. Before 1054 the Roman Catholic and Eastern Orthodox Churches were one, but their practices were significantly different well before that formal Schism.

Let's step into an Eastern Roman Parish in, say, the year of 700. This was only eight years after the Quinisext Council, so its a good time with pretty concrete historical records to look at how things are for lay people. Any Orthodox Christians may recognize that the majority of what they read here is not much unlike what they experience today.

As always on Church History, I state up front that I am an Orthodox Christian. This post should not come with any bias, but still I make the habit of putting this up front.

#General Practices

In AD700, not different from today, the congregation would come together for Divine Liturgy on Sundays. Laity who missed three consecutive Sundays or more, without a good excuse, were to be excommunicated. They would come together in a Church structure or Monastery.

#Rules for Laity

Armenian Christians had a practice of not mixing their wine with water for the Eucharist that was formally disavowed at the Qunisext Council. Laity when receiving the Eucharist were to do so with their hands shaped like a Cross.

Most restrictions against "Christian behavior" were restricted to Clergy, but some were affirmed to extend over the laity. Lay Christians were not to gamble with dice, attend the theater, consult with fortunetellers, celebrate Bota, Kalends, or Brumalia. It was against canon law to own a brothel, engage in abortion, cross-dress, or share pornographic material.

#Divine Liturgy - Sunday

Introduction

Divine Liturgy, then as now, was primarily a time of singing, prayer, and preparation of the Eucharist. It was the Qunisext Council in 692 that established the rule against "undisciplined vociferations" and admonished melodies that did not meld with the choir/congregation or were unsuitable for the Church.

The order in which things happened in Liturgy were usually formulated in Monasteries, as most higher thought in the Church did. Not all Churches used the same combination and order of Liturgical hymns and prayers, but the Rites were mostly established by AD700. the "Divine Liturgy of Saint John Chrysostom" became the most common form of the Byzantine Rite, and therefore the predominant Liturgy in the Eastern Roman Empire. It is still used today.

(If you aren't familiar with any of these phrases or words and would like me to expand, please just ask. I'm keeping it brief, as well as I can, to cover a lot of different things, and so I may accidentally include phrases that aren't commonly known outside of Orthodox Christianity or High Church Christianity.)

Liturgy of the Catechumens

Liturgy would begin, for the laity, with the Liturgy of the Catechumens; the time the nave would be open to the public. This would begin with the opening Blessing, followed by the Great Litany, First Antiphon, Little Litany, Second Antiphon, and "Only-Begotten Son".

"Only-Begotten Son" is a hymn reportedly written by Saint Emperor Justinian the Great. It was in wide use during his reign and to this day.

The Liturgy continued with another Little Litany, the Third Antiphon, and then the Small Entrance. The Small Entrance was the procession of the Gospel Book (not the same thing as the Bible). During the Small Entrance the Entrance Hymn would be sung.

Following this would be the Troparia and the Kontakia, hymns for specific events on the Liturgical Calendar. These could, and still can, vary so widely it is impossible to describe them all.

Following the Troparia and Kontakia, would by the Trisagion, Prokeimenon, an Epistle Reading, several Alleluia, and then a Gospel Reading. The Liturgy of the Catechumens ends with three more Litany: Litany of Fervent Supplication, Litany for the Departed, Litany and Dismissal of the Catechumens.

Liturgy of the Faithful

Today the public can remain in the nave for the whole Liturgy, but back in AD700 only the baptized and Chrismated could remain. At the Dismissal of the Catechumens, all others are to depart.

For the Baptized Laity, the Liturgy would continue with the First Litany of the Faithful, Second Litany of the Faithful, the chanting of the Cherubikon, and then the Great Entrance.

The Great Entrance is the procession of the Holy Gifts, the Eucharist, from the Table of Oblation through the Saint Michael Doors, around the Altar and then through the Iconostasis. Through all of this, the Laity sing and pray.

Next would be the Litany of Completion and the Kiss of Peace. The Laity is more active than just singing from here on.

The Kiss of Peace varied in practice a great deal, and still does today. The principle is that the Laity will greet and kiss one another, forgiving one another for their sins against each other.

Following this is the Symbol of Faith, a recitation of the Nicene Creed. After the Creed is completed, the Liturgy continues a bit more as the Clegy call down the Holy Spirit into the Holy Gifts to become he Body and Blood of Christ. During this time, the Laity sings along the Epinikios Hymn.

Finally, is the final string of prayer before the Holy Communion. This is the Litany of Supplication, the Lord's Prayer, and the Communion Hymn. Afterwards, the Laity would make their way to the Clergy, while singing and praying, to receive the Eucharist.

Afterward is the Litany of Thanksgiving, a prayer, a Psalm, and Dismissal.

#Life During Great Lent

The most important time of the year for an Orthodox Christian would have been the same as today; Great Lent. During Lent there were different rules and expectations for the Laity. For example, fasting on all days of Lent. It was reinforced by AD700 that the Laity may not have eggs or cheese on Saturdays or Sundays of Lent and must continue Lenten fasting on Sunday. The Eucharist, normally offered daily, was only offered on Saturdays and Sundays. There was, however, something called Presanctified Liturgy at which one could get what to the outsider would be leftover Communion.

#Other Questions & Additional Comments

The only question I think I didn't really cover is:

What would a typical person's relationship to monastic Christianity look like?

Most lay people would only interact with Monastics in few ways. When/if a lay person made a pilgrimage to a Monastery, they may encounter a Monastic. When participating in Liturgy, they were following a formula developed my Monastics. The Bishops of Cathedra were and are, at least for part of their lives, Monastics. The Church Calendar was devised and maintained by Monastics. But most lay people, outside of Great Lent, were not living much of a Monastic lifestyle.

There is more detail that can be gotten into in all of your questions, but these are the gists that I think answer what you were looking for. The summarized fact is the Orthodox Church has changed very little since the Middle Ages compared to its Western Counterparts.

#References

Canons of the Council in Trullo, also known as the Quinisext Council.

The Orthodox Faith, Volume III, Church History by Father Thomas Hopko.

Welcome to the Orthodox Church by Kh. Frederica Mathews-Green.

The Orthodox Way by Bishop Kallistos Ware.

The Orthodox Christian Church by Peter Bouteneff.