Mech maths help

Sorry for having so many posts about this but we’re in a new topic and I’m finding it difficult to keep up especially without live lessons—-

For c)i) I would have said 0m/s because I thought it pauses for a bit at the greatest height before falling again? I can’t tell how they got 12m/s

Well at least speed the vertical velocity will be zero, but what about the horizontal component?