Compatibility problems of plugin between Unreal versions


I want to start by saying that i have no experience with Unreal but we currently have no programmers with Unreal experience in our company, so I thought maybe I could start here.

We have a Unreal plugin for our device that was written in Unreal 4.21 and we build it for Unreal version 4.18-4.24. The plugin is a mixture of C++ code and blueprints. Yesterday I found out, that the plugin works fine for all versions 4.21 and above, but for versions below 4.21 I see the plugin in the plugin menu, but i can’t see the blueprints or our demo map in the content manager and I am also unable to work with the blueprints. I have a few questions now:

  1. Does it make any sense what I describe here?

  2. Is it normal that our plugin is not compatible with lower Unreal versions, even though it shows no errors during building?

  3. What is the smartest way to start fixing this problem? Is there a way to port the project to older Unreal versions or should I just restart with the plugin in an older version?

I would really appreciate any input, as I begin to learn Unreal now. If you need any more information, I am happy to help as good as possible.