Q. 1. Can a lay person give a 'reflection' or a 'talk' as a substitute to the homily during Mass?
A. 1. Only a Catholic bishop, a priest or a deacon may preach a homily during Mass. The homily may never be substituted with a 'reflection' or a 'talk' by a lay person or a minister who is not a Catholic priest (includes bishop) or deacon.
On this matter, the Code of Canon Law states:
# 766 Lay persons can be permitted to preach in a church or oratory, if necessity requires it in certain circumstances or it seems advantageous in particular cases, according to the prescripts of the conference of bishops and without prejudice to can. 767, §1.
# 767 §1. Among the forms of preaching, the homily, which is part of the liturgy itself and is reserved to a priest or deacon, is preeminent; in the homily the mysteries of faith and the norms of Christian life are to be explained from the sacred text during the course of the liturgical year.