It absolutely depends on which country are you applying to become a citizen of. Because some countries do not allow dual citizenship, so, you'll have to give up your Belgian nationality based on their request. Moreover, Belgium does not allow you to retain dual nationality if you want to become a citizen of some countries such as the Netherlands, Korean Republic, and Japan.
You can apply for dual citizenship to the USA and almost any other country. Many more people than you might think hold dual citizenship. But the road to dual citizenship, with only a few exceptions, is long, twisting and full of "gotchas".
No husband has to apply again for himself because shared visa like spouse can be granted or extended but not the citizenship for an individual.
Yes, you can apply for German citizenship and be a dual citizen regardless of the fact if your mother was still a German citizen or not.
India does not allow dual citizenship. But you can apply and get a passport-like booklet, at the nearest embassy and consulate general, that will allow you to travel to India visa-free.
Not unless you renounce your Canadian citizenship voluntarily.
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.
The US recognizes dual citizenship.
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.
India does not allow dual citizenship.
Yes, Thailand allows dual citizenship.
Dual citizenship is when one has citizenship rights in two countries.
No difference in the meaning but when people talk about Immigration and citizenship topics, almost all of them use the term 'Dual Citizenship'.