It depends on the country and the situation. Some countries require that you give up one of your citizenships. Also, if you have citizenship of a country that requires you live (or at least return) for a set period of time (as in you visit at least once a year or live there for a certain number of years per number of years you live outside of the country) and you live outside of said country for too long, you may lose citizenship (note: some citizenships allow that you live outside of the country indefinitely).
Not unless you renounce your Canadian citizenship voluntarily.
no you won't, you will have a dual citizenship which ok, but you can't swear to both countries
He will become a dual citizen of the uK and the US.
Yes, both countries allow dual citizenship. However, if you live more than ten years outside Ireland, you will lose your Irish citizenship.
Vietnam does not generally recognize dual citizenship. Vietnamese citizens who acquire foreign citizenship automatically lose their Vietnamese citizenship. However, there are certain exceptions, such as for individuals who hold citizenship of countries with which Vietnam has agreements that permit dual nationality. In practice, this means that while dual citizenship is not officially recognized, some cases may allow for it under specific circumstances.
If you apply for citizenship in another country your US citizenship is automatically revoked. The US does not recognize dual citizenship. You revoke it in writing at a US embassy, outside the US.
Typically the child will have dual citizenship until they reach the age of 18, at which point they have to determine which citizenship they were going to go with.
No.
The US recognizes dual citizenship.
India does not allow dual citizenship.
Yes, Thailand allows dual citizenship.
Yes, Poland allows dual citizenship.