What is the difference between cuarto de baño and aseo and servicio and retrete ?Feel free to just provide example sentences.

No difference. In the past, etiquette required that you avoid mentioning the toilet, because it was regarded as a dirty word, so eventually a new euphemism was created to replace the old "dirty term", but of course, the new "cleaner term" eventually became dirty and another euphemism was created. Because of this, you can say:

cuarto de baño (even if there is no lavabo inside)
baño
aseo
servicio
retrete (not considered elegant nowadays)
lavabo (even if there is no lavabo inside)
váter (nowadays it sounds bad, from English water-closet)
evacuatorio (rather old fashioned)
escusado (a bit old fashioned)
urinario (nowadays it sounds bad)
necesario (rather old fashioned)
común (rather old fashioned)
sanitario (not used everywhere)
privada (very old fashioned)
secreta (very old fashioned)
jardín (old fashioned, used especially in ships)
servidumbre (extremely old fashioned)