About mouthwash - where I live people do drink it to get drunk. Stores are warned to not sell mouthwash to people who look like they may be a substance abuser. How does staff decide who is and isn't an abuser - that I don't know.
The McDonald's hot coffee case is a pet peeve of mine. My first...
You met the criteria to study abroad and therefore you earned it.
The other students may not understand you. They probably don't feel contempt/hatred towards you. If they do, that is their shortcoming.
People are often jealous when someone else succeeds.
Please don't let that dumb teacher...