When people ask you a question you don’t know, its ok. You are not supposed to have all of the answers.
I have seen that people with big ego think that they need to be perfect all the time. Perhaps if you are a genius you might be perfect more than us mere mortals. However even if you are a genius, being humble is more helpful.
Why? Things change. An answer that was true yesterday may not be true today. This is especially true with products that are constantly being improved like software.
When someone asks me if something is possible in IT if I don’t know I say I will find out. If I know its possible I will tell them yes. We don’t have to play games with people. We can be honest and direct.