if the webdev 24 server was configured correctly at install, then yes, no problem.
When installing, there is a question asking if you wznt to support OLDER version of the webdev engine. If answered yes, then ALL older webdev enginbes are installed too, and your webdev 20 website will be managed by the older engine.
You can check that in IIS where one entry per engine is visible.
If this option was NOT checked at the time of the install, then the webdev server will need to be RE-installed, as it's the only time that this option is available.
I have used this many times without any problem (again, IF configured correctly)