What is the difference between a fraudulent, forged, and fake university degree, and what is the ruling on dealing with each of them?

There is no difference in the ruling between a fraudulent, forged, or counterfeit certificate. Deception, forgery, and falsification are not permissible in Islamic law, due to the Prophet's (peace be upon him) saying: "Whoever deceives is not one of us." If a person repents from the deception and is proficient in the job they perform, then there is no harm in them taking wages for their work.