No. That is not legal in any European country.
No, you can only be married to one person at a time.
He married in another state and didn't know he was still legally married to someone else
If you are married under the laws of another country, you are considered married throughout the world. If you have one wife, you cannot legally marry another. It is bigamy and is against the law in the United States.
If the marriage is legal in the other country, they are married everywhere in the world.
If you have a copy of your paperwork, your marriage is legal.
As long as you have the legal documentation to prove you are married your marriage shoud be held valid in any other country. (there are some exceptions; for example in some countries polygamy is legal, but not in others)
You can find the countries where polygamy is legal in the link below. However, you must relocate. If you are not from that country and just go there to get married it will not be legal if you return to a country where plural marriage is illegal. In Western cultures you can only be married to one person at a time. The single exception if Saskatchewan.
No. I don't think it would be legal. I know people go to Mexico for divorce, but there is special paperwork and requirements that they meet. But, if you wanted to go to Germany for divorce I don't think you could. The laws there are German, not American law.
Even if you are pregnate while a minor you still need to get a legal guardans approval before you can be legally married in general, but if you go to another country to get married, and are NOT a legal citizen of that country, it would not be a legal marriage.
It is until you have registered as a married citizen in America.
No. Aside from passports, some countries don't recognize weddings as legal with or without legal papers, including changing your last name.
No. Civil Courts, with the exception of immigration courts are limited to legal citizens, aliens and those legally in the country.