My question is that is it good to place multiple question on same topic in same question or is it good to post them seperately?
Generally speaking unless the questions are closely related, then they should be posted separately. By closely related I do not mean 'about the same movie', I mean that the questions are linked such as answer to the first question may impacts the answer to the second.
The questions here are not particularly related, the salary of an IMF agent is not related to why Phelps did not kill Ethan on the train - so they clearly should not be posted together.
Asking any number of questions on the same movie in separate posts is completely fine.