The most common type of plastic golf balls are plastic dimpled and plastic with holes and HDPE foam types are legal. As long as they are commercially marketed as "plastic practice golf balls", they may be used. It is recommended that students bring the packaging if there is a question.
Rule 4.d. explicitly says that the target is either tape on the floor or panels lying on the floor. There should not be any significant difference between the floor height in the launch area and the targets.
Competitors may choose either target for their first shot. They may then choose to take their second shot at the same target or their first shot at the other target. If they qualify to take a bucket shot after their first shot at a particular target, they must ask for the bucket when they wish to take the second shot at that target.
Rule 4.i states that "making contact with the inside bottom surface is worth an additional 100 points." It does not state that after making contact the projectile must remain in the bucket, so the bonus is given even if the projectile subsequently bounces out of the bucket.