Question 1 - Middle
Placing 2d in the back row eliminates your flush potential in the back.
Since 2d is a throwaway card, the middle row may be a slightly better choice since it is the MOST empty row, so that it can act as a pair catcher.
Question 2 - Front
Placing 9d in the back row eliminates your full house potential in the back.
Placing 9d in the middle row concedes the row, which is still alright in this case unless the unlikely scenario of you catching two more 4's AND fulfilling your full house draw in the back row.