Any of them. 1/3-stop makes about a 10% difference in the DoF, which is essentially imperceptible.
As above. Obviously there's a quantifiable difference, but a practical one? No.
From the bokeh quality wide open perspective, was this shot at f/1.2 or f/1.4?
View attachment 185991
Which of the two images below was shot at ISO 4800, and which has the image quality degradation that is evident at ISO 6400? (Note: same camera for the two images.)
View attachment 185992
View attachment 185993
When you look at files from the EOS M5 and the EOS M100, can you tell that the M100 has 1/3-stop more DR at ISO 100? The 5DIV has a diffraction-limited aperture of f/8.6, if you take an image at f/9 vs. f/10, will you see the difference in sharpness?
These effects — bokeh, DoF, image noise, diffraction — change gradually, there is no 'cliff' at which the images transition from good to bad. The magnitude of change with 1/3 of a stop is just not that great.
About the only situation where I think 1/3-stop can make a practical difference is shutter speed, for example 1/2000 s may not be fast enough to freeze the wingtip motion of a bird in flight, whereas 1/2500 s may do so.
I'll post quiz answers tomorrow...