Answer: 1 The Little Prince is worried that the sheep might eat the rose. 2 a rose and a baobab. 3 The crazy (actually lazy) man did not keep the baobab tree on his planet under control, so it grew so large that it destroyed his planet.
There is another man so busy with "serious" business that he neglected to think about the conflict between sheep and roses, or why roses have thorns...
Explanation: This part is more complicated: 4 The Little Prince wants to see the rose. The rose is temperamental and proud. She tells him to go away. 5 She does not want him to see her crying. (at the end of chapter IX)
There may be other reasons. The Little Prince goes on a voyage that takes him to other asteroids and eventually to Earth.