andrewb
I suggest going with the latest. If you find anything does not work in an older version, I don't think anyone will fix it.
If you want to use a safe method, reinstall all apps.
You can do it in the same partition. Rename the tce directory to something else, and start again with a new tce directory.
I run multiple versions of Tinycore in the same partition. You can go back to an old one if something does not work, which is good for testing release candidates, or experimenting with modifications.
http://wiki.tinycorelinux.net/wiki:updateIf you have your home and opt backed up, you can't lose data.