We currently abort compilation with a helpful error message for unsupported Haxe or SWF versions - it would be nice to have the same for OpenFL and Lime. However, I'm not sure what versions are still universally supported across the Flixel libs (testing this is quite annoying due to the download size of Lime).
We do have compatibility code in place for at least OpenFL 3.4.0.
Looks like we don't support OpenFL 3.4.0 / Lime 2.7.0 (even though there are still conditionals for it) anymore actually, there's a compilation error on Flash.
We currently abort compilation with a helpful error message for unsupported Haxe or SWF versions - it would be nice to have the same for OpenFL and Lime. However, I'm not sure what versions are still universally supported across the Flixel libs (testing this is quite annoying due to the download size of Lime).
We do have compatibility code in place for at least OpenFL 3.4.0.