Devotion to the Guardian Angel: how many Angels are there and what do they do?

According to all the authors, there are nine choirs of angels:
1 - ANGELS, which appear in many biblical texts (Ap 5, 11; Dn 7, 10);
2 - ARCANGELI, especially St. Michael, Gabriel and Raffaele (1 Ts 4, 16);
3 - PRINCIPALS (Eph 6, 12; Col 1, 16; Rom 8, 38; 1 Col 15, 24; Ef 1, 21; Col 2, 15; Col 2, 10; Ef 3, 10);
4 - VIRTUE (Eph 1:21; 1 Pt);
5 - POWER (Same texts as the Principalities);
6 - DOMINATIONS (Col 1:16; Eph 1:21);
7 - THRONES (Col 1:16);
8 - CHERUBINI (Ez 10, 1-20; Gn 3, 24);
9 - SERAFINI (Is 6, 2-6).

According to the revelation made by God to the German mystic Mechtilde Thaller (1868-1919), the Principalities are entrusted with the care of the parishes and all their faithful. I am always in adoration of the Blessed Sacrament, day and night, and pray for the faithful of the parish. No priest should forget to greet the angel of his parish and the angels who surround and worship Jesus before the altar of the parish.
Virtue angels push towards virtues and embody them in different ways. Some of these angels are particularly distinguished in some virtues, for example: in purity, faithfulness, generosity, patience, joy, hope. For this reason, it will be more than appropriate to ask the angel Purity for this virtue, or to the angel Cheerfulness, who will give us the joy needed to free us from sadness. And in the same way we can behave with other virtues; especially with those we most need.
The Power angels accompany their priests in religious services, especially when they celebrate mass and confess ...
Domination angels are angels who especially protect missionaries for the glory and enlargement of the kingdom of God. They are the angels of teaching, even in universities, in the spiritual direction…
Thrones are angels of the royal category, since they are angels who help and assist kings and their high dignitaries.
The Cherubim are the swords of God, swords of fire and stand before the throne of the Pope and before certain shrines to protect them.
The Seraphim are love angels, who are at the service of love. They relentlessly adore and love the Holy Trinity. They were created to love and worship God. They are the most spiritual, the most loving angels: they are full of the fire of God's love.
Perhaps these ideas by Mechtilde Thaller are questionable, but what is certain is that there are choirs of different angels, who maintain distinct missions and with each of these choirs it would be nice to make friends so that they can help us throughout our lives.
For my part, from time to time, when I celebrate mass, I personally invite one of the angelic choirs, so that, on different days, I can keep my special company and, normally, I invite them all to stay with me while I celebrate mass ( 3).

Their functions
We know that there are angels protectors of the Nations, as many Holy Fathers teach as early as the fourth century, such as the pseudo Dionysius, Origen, St. Basil, St. John Chrysostom, etc. St Clement of Alexandria says that "a divine decree distributed the angels among the nations" (Stromata VII, 8). In Daniel 10, 13-21, we speak of the protective angels of the Greeks and Persians. Saint Paul speaks of the protector angel of Macedonia (Acts 16, 9). St. Michael has always been regarded as the protector of the people of Israel (Dn 10, 21).
In the apparitions of Fatima the angel of Portugal is manifested three times in 1916 saying to the three children: "I am the angel of peace, the angel of Portugal". The devotion to the holy guardian angel of the Kingdom of Spain was spread in all parts of the Peninsula by the famous Spanish priest Manuel Domingo y Sol. He printed thousands and thousands of report cards with his image and the angel's prayer, propagated the novena and founded in several dioceses the National Association of the Holy Angel of Spain. This example also applies to all other countries in the world.
Pope John Paul II on July 30, 1986 said: "It can be said that the functions of angels, as ambassadors of the living God, extend not only to every single man and to those who have particular assignments, but also to whole nations".
There are also guardian angels of the churches. In the Apocalypse, the angels of the seven Churches of Asia are spoken of (Rev 1:20). Many saints speak to us, from their own experience, of this beautiful reality, and say that the guardian angels of the Churches disappear from there when they are destroyed. Origen says that each diocese is guarded by two bishops: one visible, the other invisible, a man and an angel. St. John Chrysostom, before going into exile, went to his church to take leave of the angel of his church. St. Francis de Sales wrote in his book "Philothea": "They become familiar with angels; they love and venerate the angel of the diocese where they are found ». Archbishop Ratti, the future Pope Pius XI, when in 1921 he was appointed archbishop of Milan, arrived in the city, knelt, kissed the earth and recommended himself to the guardian angel of the diocese. Father Pedro Fabro, Jesuit, companion of St. Ignatius of Loyola, says: "Returning from Germany, while passing through many villages of heretics, I found abundant consolations for having greeted the guardian angels of the parishes where I went". In the life of Saint John the Baptist Vianney it is said that when they sent him pastor to Ars, glimpsing the church from afar, he got down on his knees and recommended himself to the angel of his new parish.
In the same way, there are angels destined to the custody of the provinces, regions, cities and communities. The famous French father, Lamy, speaks at length about the protector angel of every country, every province, every city and every family. Some saints say that every family and every religious community has its own special angel.