High School:
If you have a run for a first down and (1)during the play there is an unsportsman-like penalty on the O or (2) there is a dead-ball unsportsman-like on the O, what are the resulting situations?

1st and10 until the ready for play.
 

Any nonplayer and unsportsmanlike conduct penalties are enforced first, then the chains are set 1st and 10. Once the chains are set and the referee marks the ball ready for play, if an USC foul by A occurs then you would have a 1st and 25 situation.