Can a normal pulmonary function test (spirometry test) rule out COPD and emphysema?

Yes. You will have abnormal lung function test if you have COPD or emphysema. Do note that smoking is not good for you at any amount and some genetically-susceptible people may get emphysema even with light tobacco exposure.
Yes.... In copd, there is chronic obstruction in the airways. In a pulmonary function test, it will reveal this obstruction. If there is no obstruction on the pft, then asthma can still be present but not copd.