From my understanding, if you make a reply and someone make a question after your reply, you can reply that even your previous post has been a few minutes ago.
If the last post has been made by you, you can only edit that.
You can bump your thread after 24 hours. But you should delete the previous post.
Not sure if you have to remove the previous bump if it's a legit reply to someone.
To be safe, I suggest to copy the previous post, make a new one, paste the previous post and then add what you want.
Please someone correct me if any of statements is wrong