I use Ubuntu, so I'm not sure about the particulars of Fedora. Perhaps
Fedora Forum may be of more help.
That said, my personal upgrade
philosophy is: "don't". There will probably be some cruft left over from the old version and if the new version doesn't work, there's no way to get your old working system back.
I prefer to get a new hard drive, install the new OS and either use the old drive as a slave and mount the old data in my new home, or just copy the data over.
If you don't want to fiddle with hardware and have some free space on your hard drive you could play games with partitions, like create a partition for the new OS, leave one for the old and possibly another partition just for data.