The old Catholic Encyclopedia doesn’t explicitly cite canons on the matter, and predates the Pio-Benedictine
CIC, so I’m not sure if we can definitely rule out two steps, but it does say there should be an odd number:
In the beginning altars were not erected on steps. Those in the
catacombs were constructed on the pavement, and in churches they were usually erected over the
confession, or spot where the remains of
martyrs were deposited. In the fourth century the
altar was supported by one step above the floor of the
sanctuary. At present the number of steps leading up to the
high altar is for symbolical reasons uneven; usually three, five, or seven, including the upper platform (
predella). These steps are to pass around the
altar on three sides. They may be of wood, stone, or bricks, but St. Charles (Instructions on Ecclesiastical Building, xi, no. 2) would have the two or four lower steps of stone or bricks, whilst he prescribes that the predella, on which the celebrant stands, should be made of wood. The steps should be about one foot in breadth. The predella should extend along the front of the
altar with a breadth of about three feet six inches, and at the sides of the
altar about one foot. The height of each step ought to be about six inches. Side altars must have at least one step.
newadvent.org/cathen/01356f.htm