Developping a Plugin for Trados

We are IT company and would like to develop a plugin for Trados Studio 2019. I have two questions : 

- once the plugin is done, can we send it to all our freelance translators around the world who are using Trados ? will they have problems with installing and using it ? does the plugin have to be approved by SDL ?

- if the plugin is developed for Studio 2019, will we be able to use it in previous or later versions of Trados ? If not, is it complicated to upgrade out plugin in order for it to be compatible with future Trados versions ?

Thank you very much for your help.