From ONE parent is enough.
No, the legal age in Virginia is 18.
Nope, not in any state.
Transporting a Minor across State lines is a Federal Felony Crime no matter what the reason. Typically a minor requires parental consent to get married. Without it, the marriage will not be legal. There are a few places that would allow a the marriage with a court order, but not likely to be issued if the parents do not consent.
From ONE parent is enough.
Generally speaking, a minor cannot get married without consent. If the parents are dead, the legal guardian will have to consent to the marriage. In some states, it is possible for a court to grant permission for a minor to marry without parental consent in certain circumstances (for example, in the event of a pregnancy). Since marriage laws vary from state to state, you'd need to specify where you are for a full answer.
None of them and in some you also need the courts permission apart from your parents.
In states where same-sex marriage is legal, the same requirements apply to all who apply for a marriage license. If a minor can marry with parental consent in your state, then the same will still be possible after same-sex marriage is enacted.
If her parents consent to the marriage, yes.
That will depend on the specific state and situation. If only one parent has custody, that parent must consent. Check with your marriage license issuing authority for the exact requirements for your county.
Yes there are no laws for dating. For sex you must have reached age of consent and in Virginia that is 18 but in Virginia it is illegal to have sex outside of marriage.
No, a marriage is legal only if it adheres to the laws of the state in which the marriage takes place.
That depends on the state. In many states, if both parents have equal custody, then both signatures would be required.