No, it isn't, and leaves you with a range of options to follow.
What if someone forged or copied your signature to a divorce decree authorizing Or requesting a name change
No. The word "forge" specifically indicates the illegal misrepresentation of oneself.
No, they cannot legally sign. They are not considered to have the capacity to contract as a minor.
You can't. Marriage is a legally-binding event which requires you to sign legal documentation. This is not possible over the internet.
online you can look up public records for your specific county (provided they are online).
Think about the question you just asked. If you are still legally married - then you are still legally married. You can not be single and married at the same time. Separation is not divorce. In order to be single, you must get a divorce. ---- And, even if divorced, you're not single. You're either a Divorcee (female) or a Grass Widower (male).
If the separation is legally binding, then no you can not file adultery. If there is no legal separation, you can claim that you were working on your marriage then with a lawyer, you can file adultery.
No. You must be completely and totally legally divorced, first.
If the marriage is not done by someone legal such as a minister; pastor or justice of the peace and the person who married the two of you does not have a license to do so then you are not legally married and so no divorce is necessary.
Contest it how and why? I am going to have to assume that you are saying someone died and had a girlfriend or someone else as the beneficiary on a life insurance policy and not his wife. If this is the case she can try but she will not be successful in contesting it. A life insurance application and policy make up a legally binding contract. If he did not put her as beneficiary it was because he was forgetful or didn't want to leave her the money. In either case the court will side with the only evidence of his intention which is his last beneficiary designation which was signed and witnessed and is legally binding. She will be wasting legal fees.
Have sex with WHO? Your spouse - yes, of course - you're still legally married. With someone else - at your risk - you are still legally married and could be charged with adultery. Also, you run the risk of having this produced during your divorce proceedings.
Before someone can get married again they must have a finalized divorce decree from the first marriage. Without that the second marriage is not valid.