Not at all. "Gay" is the preferred term for someone who is attracted to members of the same sex. It is inappropriate (the not illegal) to use "gay" to mean "stupid."
The word "homosexual" is now considered inappropriate (but also not illegal) to use as a noun in English-speaking countries, as it has a clinical connotation, and is also frequently used by those who oppose gay rights.
No, it is not illegal, but it is quite ignorant and hateful.
No, however, attempting to insult someone by calling them gay is ignorant.
Yes.Technically, only homosexual acts are illegal, but if a person is suspected of being gay, they can be prosecuted even if no homosexual acts occurred.
They call the gay person by his or her name. If they don't know the name, they'll say sir or madam.
Depends on the country. it is not illegal in the United states, but as of 2013, 29 states can fire a person just for being gay, regardless of the profession.
Paradise.
they usually call them by their names, but I think the term you're looking for is "gay".
Interview for a job? The same way you interview anyone else. As of recently, it is illegal to discriminate if you are gay.
Yes, although if a gay person is not sexually active, he or she has little chance of being arrested.
No, it is not illegal, but it is ignorant and hateful.
Gay
Calling someone gay as a term of abuse is offensive and illegal in many countries. Bullying and cyberbullying similarly.