In many cases, it's a good idea to leave out the ending. This gives readers the chance to form their own expectations and keeps the mystery intact. But for some novels where the ending is unique or sets the story apart, a hint might be okay.
Fan Xian did not explicitly state that he would not use the back door or leave a way out. Although he had an upright and kind personality, he was also a smart and quick-witted person who would make corresponding decisions according to the situation. Fan Xian displayed his wisdom and ability in the play. Through his own hard work and talent, he successfully achieved success in the court and in the martial world. His choice was correct, and he would not leave a backdoor for others.