My friend wants to upgrade his F31 box to F35, using the dnf method. Can someone recapitulate that for me?
Thanks.
Be aware that you can only skip 1 version, so you should upgrade from 31 to 33, and then from 33 to 35.
Skipping more than 1 is not recommended and not tested.
Also, I suggest to keep your system upgraded in future as there are no (security) updates available for versions older than the current two releases (currently, 35+34). This should not be underestimated, especially if you use the system on the Internet.
If your question is the difference among different upgrade methods, you can start comparing them here: Upgrading to a new release of Fedora :: Fedora Docs
No updates of any kind, security or otherwise.
Nothing else I wanted to say, hence the brackets 
I just wanted to focus on the security updates, which I see most critical in outdated systems. Sorry for the misleading spelling 