But how? 3.2 RC was not released. See: GIMP - Development Downloads
As long 3.2.0-RC(1) is released there will be no 3.1.7 but 3.2.0-RC2.
Yes, at least for ImageChooser. I have asked numerous times already. See last one here. Or here.
Hmm… The GL issue you linked is not labeled as bug on the API so indeed is unlikely to be implemented any time soon. All depends on the 2-3 C developers we have