Confusing myself in preparation for a job interview

The difference between discreet and discrete is discreet, but the difference between discrete and discreet is discrete. 

Affect can effect an effect, but can an effect affect an effect?

Should we hear hear here? Can we hear hear hear here?

Can I have fewer 'less hairs' and less 'fewer hair'?

The stationery stationary on the station. The station with the stationery stationary.

Do I have license to practice, or should I practise licence?