In a game of "jacks or better" to open, player A opens. He draws one card, then declares a win with a pair of sixes and a pair of threes. since he could have drawn one of the pairs, is his hand a winner?
Yes his hand is a legitimate opening hand thus the winner. Two pair is a legitimate opening hand, there is no practical way to determine if the player did not draw one card to a pair and kickers to make two pair. However we can safely assume that he was indeed drawing to two pair, if he drew one card than turned up the two pair at showdown.
There are no common sense situations were a player would open with one pair and draw one card. It is a horrible play, its cheating with a downside. So in a practical sense no one should even care if you opened with one pair and drew one card.
Not a real good question, it rarely if ever happens and has almost nothing to do with a real world scenario.