In an interview, should I greet a professor I know in one of his speech?
Since everybody felt compelled to comment rather than answer, I'll summarize the comments (none of which are in favor of your idea) as an answer (CW, since it isn't "my" answer).

The commenters seem to think that your "connection" to the professor will not make any positive difference. From Anonymous Mathematician:


  I'd bet you're overthinking this, and that it won't really matter whether you greet them by name or remind them that you asked a question... They'll probably just assume you've seen them give a talk or read about them online. Professors are often used to being recognized by people they don't know (for example, almost everyone who teaches large lecture classes experiences this, and the same is true for a plenary speaker at a big conference). 


And that your attempt to remind the professor of the "connection" might make him feel uncomfortable or seem unprofessional. From RoboKaren:


  I have a terrible memory for names and faces.anyway. In a situation like this, I'd be worried that you were trying to curry my favor (which is exactly what you are trying to do, I think), so I'd be more worried than pleased or curious.


And, asking about this professor's advisor (rather than his research) at his talk sounds like a terrible idea. From Alexandros:


  Do not be creepy, in your effort to impress people. Be polite and professional and stick to questions that matter to your research... Asking someone twenty or more years later, about their PHD advisor, sounds creepy to me. Ask them something that is related to your research. If you cannot find a suitable question, simply do not ask anything. Sometimes it is better to keep our mouths shut than someone remembering us from some silly / creepy thing we said. Memorable is not the same as favorable.


Finally, if you do insist on reminding this professor that you attended his talk, JeffE advises not to make a big thing of it:


  "Hi, Professor [Name]. I don't know if you remember me, but I attended a talk you gave at my university a few years ago. It's nice to see you again." Then stop and let them respond. If they don't mention your question, they probably don't remember it; let it go. 


Finally, I'll add my own take. You say "I don't intend to play a psycho game with them." That seems wise. I suggest you refrain from playing any games. Concentrate on making a good impression solely on your research ability and professionalism, and forget about any "tricks" that you might feel compelled to try - these are more likely to hurt you then help you. 

(Note that the other "tricks" you've suggested here and here did not go over well, either. That's not a coincidence. The people evaluating your applications are trying to do their job: to hire/fund/accept the most qualified individual. Gimmicks that don't help them do that job are not going to be appreciated.)