There is basically no failure in thesis defense, as long as you do a good job in the process of changing. The defense teacher will only let you briefly introduce your paper and then ask you two or three simple questions. 20 minutes at most. When I defend, I only have 10 minutes. If you want to apply for a bachelor's degree, at the end of your defense, you give the defense teacher a hint and tell them that you want to apply for a bachelor's degree, so they won't embarrass you, and basically they will give you good grades and above. Good luck.