there are no fixed answer for these questions , the answer here depends on your own experience , u should talk about urself as my answer for these questions will be completely different of yours
just tell me your answer according to ur previous experience and i can help you to Formulate it properly
for this question : tell me briefly .when you face stressful situation and how did over come ??????
try to talk about hard situation which is happened during you previous job , if you don't have a work experience talk about a hard situation in ur life as something hard happened to your family or friends and you were a part of the problem and how you deal with the situation
for this questions: are you flexible person . and how ?
you must be a flexible person if you intend to be a flight attendant , flexible mean that you are able to work in different atmospheres with different people from different backgrounds which is mean that you are adaptable person
so if your answer is that you are flexible person, the prove will be that you don't mind working with a group
of various Mentalities and you respect the differences between people
you can enhance your answer with an example of your previous work experience
for this question : tell us about most difficult thing u see in your point of view ?
this is a purely personal question aims to show how you evaluate things
so try to talk about something related to the job you applied for, such as the disability of saving someone's life
hope that i have helped you to answer the questions &good luck