Apply at the nearest embassy or consulate of your country of citizenship.
*Your case would not be approved usually if you do not have another citizenship.
No - citizenship is not transferable from one person to another !
Yes only if that person is a American applying for dual citizenship in Brazil. A person from Brazil would be unable to keep citizenship in Brazil if they wanted US citizenship. because the US requires you to give up your citizenship to all other countries except Canada citizenship.
If you "renunciate" something, you give it up.
expatriation
It depends on the countries they want to be a citizen of; whether they allow multiple citizenship or not. For example, one can have British, Canadian, America, Australian and Italian citizenship at the same time because all allow multiple citizenship. But, if the same person wants to become a German citizen, they must give up all five before doing so.
give up your Indian citizenship
It depends where his parents are from. If a child has US citizenship,the US does not require him to give up the US citizenship ever. But, let's say the parents are from Japan, government of Japan requires him to choose between Japanese or American nationality and give up one of them.
If he is a US citizen that happens to be in Turkey, then yes. If he has Turkish citizenship, he will need to attain US citizenship (either dual citizenship or give up his Turkish citizenship for an American one).
It's sort of hard. :)
Americans can live in Canada if they apply for permanent residence. They do not, however, need to "give up" their citizenship and may apply for a dual citizenship. They will have both a Canadian and their American citizenships.
She can, but she will have to give up her US citizenship, not a good idea.
A person can lose their citizenship voluntarily (i.e) on their own wish. If citizens act in any way that is against the laws of the country, then the Government of that country can strip the person's citizenship status. Not all criminal offence lead to the losing of citizenship.