I have seen some old posts where:
- The given links are not working
- The posts say a module is not available for a given Drupal version, but the module is now available for that version
How can I edit/improve those posts?
For posts using a link that is not working anymore, you need to check the following.
If the post is still understandable without the link, I would remove it. If there is a link that can replace the old one, I would edit the post to change the link; for example, this is what can be done for links to documentation.
If the post is a question, which is not anymore understandable without the link, then the question should be closed. Questions should be helpful to the user who asked it, but also future users; if future users don't understand the question, they cannot even understand the answers, and this makes the question not helpful for them.
As for answers saying that a module is not available, just add an answer saying that the module is available. Keep in mind that questions about modules are now off-topic. if the question is asking for a module with the same functionality available in another module that is available for a different Drupal version, chances are the question should be closed.