Sometimes when I want to ask a question, I see it is already exists, but its answers are old and might not be relevant.
Is the best approach to ask a new question, or use the original one by posting a comment?
If you see the answers are not relevant for those old questions, you can ask you question stating you have already gone through this old question and found that the answer is irrelevant.
Then, the community will act on your new question and start posting answers if they feel the answer for that old question is really irrelevant. Else your new question will anyway be closed as duplicate ;)
Some things you could try:
In short, it's the same process I think anyone should go through before asking a question: make sure they understand in as much detail what the problem is.
If you get to the end of that process and you've found something that you don't understand or something that looks like it has changed, I don't see why you shouldn't ask.