So you have a couple of issues to address here.
Dealing with people who are older then you.
The person older then you is going to have more experience (certainly more life experience). They will also have different expectations of what to expect from a manager.
So you need to set the expectation of your experience with them. I would recommend to start off with something like. "I have been in this role for [insert time] so what I am going to show you is more company process and why the company does X a certain way".
Older people may have dealt with different managers, so they expect you to lead rather then come with "I don't know".
There is a quick way to see if this is the case. If the person comes with a problem and expects you to solve it, then they have not had much manager interaction/experience (cover that later).
Example: "I ran the program but it is giving me error XYZ. What do I do?"
On the other hand, if they come to you with a problem and detail what they need to solve it then they have had experience with managers. In this instance you see what resources you can offer to help them. If it is outside your ability to give, point them to their manager.
Example: "I ran the program but it is giving me error XYZ. Can you tell me where I can get the error code list?"
Managing people in a non-management role.
The number one point you have to realise is that you are not their leader, nor manager. You do not have the ability to boss them around. So if a situation arises where rank has to be pulled, you need to refer them to their manager. Don't get involved with it.
You are there to grow their skills in the areas they are not aware of, and focus on that.
Where the person comes to you on how to solve a problem, I would recommend reading up on the GROW model. It is a technique to teach them rather then keep coming back to you like a search engine.
This can be a case of answering their questions with questions that lead to the answers. You get a better understanding of where they are at.
Them: "I ran the program and got error XYZ. What do I do?"
You: "What is the details of that error message in the manual?"
Them: "I don't have a manual".
... So the actual problem is they don't have the manual. Get them the manual. However if you know the answer isn't there, then read the answer with them and then explain how you find more information from there.
The main point is don't just answer their question (even though it is tempting).
Dealing with people with a technical stronger background.
This combined with the others can be the most troublesome. As mentioned earlier you set your expectation of your technical area, so they know where your leadership line ends.
If they start to question why something is done a certain way, avoid "Because it is always that way". Try to explain why that is, or refer them to management or a senior person if it is outside your expertise.
Likewise if they ask numerous technical questions on how the system works vs other systems (technical knowledge). Acknowledge that the question is a good one and that it is outside your area of expertise.
I can't stress enough be honest that is outside of your expertise. I would even go so far as to tell them that what they mentioned is interesting and write it down (to read up on later).
If they continue to interrupt in such a manner, ask them to make a note of the questions and you can find the answers for them offline (if in a training scenario).
The main point is not to get into confrontation with them on technical issue. Instead defer.