How many and which versions of QGIS should I use to test a plugin?

Greetings I’m working on a plugin. I’m developing it in QGis 3.4 and now testing it in QGis3.0 (with several bugs).

With these two versions is enough if I want it to be approved in the repository? I don’t want to uninstall and install new versions, it’s a risk.
What are the requirements? Minimum versions?