In a line with Venus and Earth on the same side of the Sun because we must be as close to Venus as possible because it is so small in our sky.

Venus is always in a 'Full' phase because it is closer to the Sun than the Earth.

In a triangle with the right angle at the Sun

In a line with Venus and Earth on opposite sides of the Sun because we must be as far away as possible from Venus to see its 'Full' phase.

In a line with Venus and Earth on opposite sides of the Sun because we must be in a position where we can see Venus fully illuminated by the Sun.

In a line with Venus and Earth on the same side of the Sun because if Venus were on the other side, the Sun would block it out.

Venus does not have a 'Full' phase.