In the United States anyone can sue anyone for any reason. The answer to your question is yes. Finding a lawyer to take your case is another story. Finding a judge who will not throw your case out of court is another story. Finding a judge who will not consider your lawsuit frivolous and order you to pay all sorts of money is another story. But, yes you can sue.
Answer
In order to sue you need a cause of action. Generally, there is no law that says parents must treat their adult children equally. In fact, throughout much of history children have been treated unequally by law. In Old England the eldest son inherited everything.
No. You have to prove the child knew what they were doing.
It is possible
If your child is 18 years of age or older, and considered an adult, then no you do not have any basis with which to sue the father for child support. That child is considered an adult by legal standards and not a dependent. Only for full-time dependents do you have any grounds for child support.
No, the child can not. The other parent could before the child was an adult. The money goes to the parent to use for the child and not directly to the child.
Unfortunently you can not in our society.
No. It is your choice to meet. There is nothing that says you have to see each other once the child is of adult age. Get a restraining order if it's so bad you feel you need to sue.
Is this a trick question? If the child is legally an adult (and therefore 'emancipated') then there is no "custodial" parent.
No, a child adult cannot do this. This has to be done when the child is under the age of 18 years old. But the child can't sue. It has to be done by the child's parent against the other parent in family court. Also depends on what state the child lives in. Family law varies from state to state.
The child can file prior to age 19.
Only up to one year past the age of majority.
Only if the obligee parent releases the claim or is deceased.
There is, if you think about it, no such thing as an adult child. If you are 26 you are an adult and if for some reason you were not supported by your biological parent as a child, it is a bit late to do anything about it now.