Ball Rolling Toward the Midline

Team A has established possession in their attack area.  A1 passes to A2, who misses the pass, and the ball rolls toward the midfield line untouched by Team B.  A3 defender, standing in his defensive half of the field, reaches over the line and 1) stops the ball and keeps it in A's offensive half without gaining possession.  2) picks up the ball and tosses it back to A2 without ever allowing the ball to cross the midfield line.  What counts do these situations create?

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