The document on the Liturgy of the Vatican Council II says, Just as Christ was sent by the Father so also he sent the apostles, filled with the Holy Spirit. This he did so that they might preach the Gospel to every creature and proclaim that the Son of God by his death and resurrection had freed us from the power of Satan and from death, and brought us into the Kingdom of his Father (No.6).
Apostle Simons name is in all the four lists of the 12 apostles in the New Testament. Simon is identified in Gospels of Mathew and Mark as well as in the Acts as Simon the Patriot (Mt 10, 4; Mk 3, 18; & Acts 1, 13) Luke says very specifically Simon (who was called the Patriot) (Lk 6, 15).
Apostle Simons name associated with the patriot says much about him. The Patriot Party (some translations call the party the Zealot) was a group of Jewish people who wanted independence from the Roman rulers. So the Patriot Party from time to time attacked the Roman rulers and their Jewish collaborators using some tactics like modern guerrilla warfare.
The Patriots consider themselves the spiritual inheritors of Maccabees described in the Old Testament. The attacks of the Patriots like the modern terrorists on the Roman rulers led to the total destruction of the Jewish Temple in Jerusalem by the Romans.
We do not have any concrete information about the involvement of apostle Simon in the Patriot Party. Perhaps he must have been a member of the party before Jesus called him to be one of his chosen twelve apostles. We are not interested about Simons role in the Patriot Party.
For us one information is sufficient that Jesus chose Simon the Patriot as one of his twelve apostles and entrusted him the responsibility to proclaim Jesus and his message.
In the Gospels according to Luke and John as well as in Acts of the Apostles we get the name of Judas as son of James. The same apostle is called Thaddaeus in the Gospels according to Mathew and Mark in their list of twelve apostles. Bible scholars believe that both Judas and Thaddaeus are one and the same person.
There are two persons with the same name Judas among the lists of 12 Apostles. Luke in his Gospel distinguishes them as Judas son of James, and Judas Iscariot, who became the traitor (Lk 6, 16).
The Catholic Christians honour Judas Thaddaeus as the saint of impossible things and lost causes. So faithful people ask for the saints intercession to get back their lost materials or to receive favours which looks impossible.
We do not have any concrete information about the life and apostolic ministry of the two apostles Judas and Simon. But according to traditional belief and the apocryphal writing of The Passion of Simon and Judas both the apostles preached the Gospel in Persia and Armenia and both suffered martyrdom at Persia.
The western or Roman Catholic Church celebrates the feast of both the apostles together on October 28 every year. All Christians believe as acknowledged in the Vatican council document on Liturgy that the Christianity is founded on the foundation of the 12 apostles. So we honour them all even if we do not know much about the life and ministry of the apostles like Judas and Simon.