After a child is emancipated by the courts and then moves back in with his mom can she go after child support again?
No, that doesn't work like divorce, and remarrying someone. The child had a court order for emancipation, making the parent's no longer responsible for that child.
I would seriously doubt it. Legally (by the emancipation) the child is his/her own guardian, so the mother would not be entitled to anything.
If the court has granted the child's emancipation, the parent is no longer a legal guardian of the child. In such case, the parent has no right to demand or go after child support because the child is essentially on his/her own.