A laicized priest should not perform any ministerial function. In this case ministerial functions would be, being a minister of Holy Communion, serving, lectoring, baptizing, and blessing.
As a seminarian comes closer to the priesthood, he is installed as a lector first, this office allows the person to bless bread and berries or something similar (It comes from the old minor orders), then an acolyte, (Acolytes are ordinary ministers of Holy Communion) then a deacon (He can bless most things), and then a priest.
As a laicized priest he is allowed to do none of these things.
A Bible study would not fall under this, though ushering may because of the old minor orders.