Is it recommended for a professor to not entertain advanced questions for a basic course?
1) How should a professor react to the most advanced questions from her students of a basic course, if (s)he knows the answer?


I would distinguish between reasonable and obnoxious questions. 


If the question is reasonable, then I would give a concise answer and encourage "offline" follow up. The question in your example seems reasonable -- it's essentially "how wide is the gap between what we're learning and what's actually used?"
If the question is obnoxious (e.g., student is just trying to show off), then I would consider giving a very concise answer (one sentence), or else explaining that you don't think the question is a good use of the available time (and, optionally, encouraging follow up in office hours). 



  2) How a professor has to react in the classroom for the advanced questions that (s)he doesn't know the answer?


I'm not sure one has any choice but to say "That's a good question, but I have no idea" or "I have no idea, and I doubt it matters for the purpose of this exam."