Can emphysema be diagnosed by mri? And will it always progress and get worse?

PFTs.., You can sometimes see signs of emphysema on MRI scans but it is typically diagnosed with pulmonary function testing. These test will show the chronic obstruction that defines copd.
Maybe. Mri is not the best way to diagnose emphysema, especially because the chest motion of breathing will distort the MRI picture. Emphysema will not always progress if you stop the cause, most importantly smoking. That said, everyone loses lung function as they age, but those with lung disease from smoking may lose that function faster, even if they stop smoking. But, still, quitting is important.
Yes and yes. Mri is extremely detailed and could detect emphysema - although high-resolution chest ct is the optimal approach. Emphysema generally progresses over time and everything depends on the onset of diagnosis - the earlier it occurs the more likely it is that one will die from the disease, the later that one will die with the disease but from other causes.