Is a player considered down if he catches a pass falls gets up and keeps going?

Answer 1

In College Football, once a player's knee touches the ground the play is whistled dead regardless of whether a defensive player made contact with the ball carrier. In the NFL, a defensive player must make contact with the ball carrier to have the play whistled dead. So to answer your question, in college the player is down and the play is over. In the NFL, the player is not down and the play continues.