Hopefully I’m not totally wrong, but restoring snapshot from 18 on 22 will reverse you back to 18, because snapshot is 1:1 copy of whole droplet.
For me spinning totally new droplet is always the last option, because I need to install everything that Ubuntu (or what ever OS) needs, including mailing system etc.
I’m totally sure that is just another trivial task for those who can, but after 10 years I’ve never learned how to start new functional droplet easily