(3) According to the properties of carbon monoxide and carbon dioxide, carbon dioxide can make clear limewater turbid, but it can't make chicken blood discolored. Carbon monoxide can change the color of chicken blood, but it can't make clear limewater turbid.

Therefore, if Zhang Qiang's conjecture is correct, then the experimental phenomena in devices B and C are: there is no obvious change in limewater, and the color of chicken blood is carmine;

If Wang Mei's guess is correct, the experimental phenomena in devices B and C are: lime water becomes turbid and chicken blood is carmine.

So the answer is: there are bubbles in B, there is no phenomenon in the clarified limewater, and the chicken blood in C is carmine;

The clarified limewater in B becomes turbid, and the chicken blood in C is carmine;

(4) Carbon monoxide is a toxic gas. When using carbon monoxide, there must be a tail gas treatment device. A pointed glass tube and a burning alcohol lamp can be connected at the outlet of device C (the tail gas at the outlet of device C can also be collected by balloons or plastic bags).

So, the answer is: burn or collect with balloons;

(5) Charcoal can reduce CuO, so it is reducible and can be used to smelt metals.

So the answer is: smelting metal.