Misc: 80's - Who sang 'Can't Fight This Feeling'?

Questions

Member of French Light Infantry corps originally formed of Algerians and retaining their oriental uniform?

In chess an obligation to move even when that move is disadvantageous?

Parallel lines made to appear not parallel by short oblique intersecting lines?

The splitting of spectrum line into several components by magnetic field?

Spirit of the times,trend of thought and feeling in a period?