The last in the test is the Sony 85mm F1.4 Planar Zeiss lens with Sony LA-EA4. With this lens being used at F1.4, I did manual focusing on the centre in magnified view with focus peaking to help achieve the sharpest focus.
1) None of these lenses seem to show any significant difference in corner performance (to me anyway_ when comparing the original vs tough E-mount. This may be as a result of them not causing any significant flexing at the mount, which could impact on image quality.
2) The tough E-mount neither improves nor degrades the image quality at the corners of the lenses I have used.
3) The corner performance of the Sony 84mm F1.4 Zeiss Planar lens is pretty impressive wide open i.e. it is sharp even in the corners.