If you have no 4 byte characters, then you can probably do an export in a way that won't lose data. But you can't know that for sure, really. Converting back is a bad idea.
In the long run, you should update your MySQL versions to 5.5.3 or later. If your hosting can't do it, find better hosting. Because they can do it. Because there's no reason not to do it. And because MySQL's "utf8" doesn't support the entire UTF character set properly, only utf8mb4 does.
If you haven't seen this video yet, take a half hour and watch it to understand more: https://www.youtube.com/watch?v=yQaRUEwEKxE