Q. 1. Can a priest compose his own 'Eucharistic Prayer' and use it during the Holy Mass?

A. 1. The only Eucharistic Prayers that can be used during the Liturgy of the Mass are those that have been approved by the Vatican. They are:

Eucharistic Prayers I - IV

Eucharistic Prayers for Masses of Reconciliation I - II

Eucharistic Prayers for Masses with Children I - III

Eucharistic Prayers for Various Needs and Occasions I - IV